Related resource: see Master's Seminary Journal article in Pdf - 2 Peter 1:16-21 The Only Sure Word

Have (2192) (echo) means to have, hold or possess and the present tense indicates that it is a continuous and abiding precious possession of all believers.

The rendering of the NASB translation (as does the ISV - see verses above) tends to suggest that the eyewitness account confirmed the Scriptures. However the literal Greek word order is crucial

“And we have more firm the prophetic word.”

This Greek word order supports the interpretation that Peter is ranking Scripture over experience.

The prophetic word (Scripture) in other words is more complete, more permanent, and more authoritative than the experiences of anyone, even the experience of the Transfiguration, as grand as that must have been. The Word of God is a more reliable verification of the teachings about the Person, atonement, and second coming of Christ than even the genuine first hand experiences of the apostles themselves! How privileged we are today to have the full revelation of God in His holy word. Oh, how we should seek with all our heart to love His law and meditate on it all the day long (Ps 119:97). Remember that it is filled with God's precious and magnificent promises!.

Vincent explains the 2 possible ways to interpret this verse

"We may explain either (a) as Revised, we have the word of prophecy made more sure, i.e., we are better certified than before as to the prophetic word by reason of this voice; or (b) we have the word of prophecy as a surer confirmation of God’s truth than what we ourselves saw, i.e., Old-Testament testimony is more convincing than even the voice heard at the transfiguration. The latter seems to accord better with the words which follow" (Bolding added)

Interestingly A T Robertson tends to favor Vincent's first explanation. I would agree with Vincent rather than Robertson for the context (specifically the next two verses vv. 20, 21) favors the latter. Why? Because Peter goes on to speak of that which makes the OT scriptures unmistakably reliable, specifically their divine inspiration which emphasizes the sure, trustworthy origin of the prophetic word. In short, as valid as Peter's experience was, the written Word of God is more sure as testified to by numerous passages...

Every word of God is tested. He is a shield to those who take refuge in Him. (Pr 30:5)

The words of the LORD are pure words; as silver tried in a furnace on the earth, refined seven times. (Ps 12:6 )

The law of the LORD is perfect, restoring the soul;
The testimony of the LORD is sure, making wise the simple.
The precepts of the LORD are right, rejoicing the heart;
The commandment of the LORD is pure, enlightening the eyes.
The fear of the LORD is clean, enduring forever;
The judgments of the LORD are true; they are righteous altogether. (Ps 19:7-9)

THE PROPHETIC WORD [MADE] MORE SURE: bebaioteron ton prophetikon logon: (Ps 19:7-9; Isa 8:20; 41:23;41:26 Lu 16:29-31; Jn 5:39; Acts 17:11)

Note that there is no Greek verb for "made", which has been added by the NAS translators. Literally the text reads "more certain the prophetic word".

Prophetic (4397) (prophetikos from pró =before or forth + phemí = tell) means pertaining to a foreteller ("prophetic"). It refers to that which was uttered (and recorded) by the prophets.

Word (3056) (lógos from légō = to speak intelligently source of English "logic, logical") means something said and describes a communication whereby the mind finds expression in words. (Click in depth study of lógos)

The phrase "prophetic word" refers not just to the OT major and minor prophets, but to the entire OT as a whole. Of course, all of the OT was written by “prophets” in the truest sense, since they spoke and wrote God’s Word, which was the task of a prophet, and they looked forward, in some sense, to the coming Messiah. In the Gospels for example we read...

And (Jesus) beginning with Moses and with all the prophets, He explained to them (Cleopas and another follower of Jesus on the road to Emmaus) the things concerning Himself in all the Scriptures (synonymous with the entire Old Testament)  (Lu 24:27).

Now He (Jesus after entering through the walls into the room where the 11 disciples were shut in) said to them, "These are My words which I spoke to you while I was still with you, that all things which are written about Me in the Law of Moses and the Prophets and the Psalms must be fulfilled." (Lu 24:44)

(Jesus speaking) "You (Jews) search the Scriptures, because you think that in them you have eternal life; and it is these that bear witness of Me (John 5:39) (Comment: The Lord was speaking of the Old Testament Scriptures, for there was nothing else at that time. These Scriptures are replete with testimonies of the coming Christ.) (Click all 52 NT uses of the word Scriptures)

More sure (949) (bebaios) (Click in depth discussion of bebaios) means fixed, sure, certain (known or proven to be true) or to something that can be relied on not to cause disappointment because it is reliable.

The idea in the Greek is

“We have the prophetic word as a surer foundation than even the signs and wonders which we have seen."

Peter is saying that...

"Here is the second line of evidence to give you confidence in what I have been saying."

Bebaios has the special nuance (taken from the commercial world) of what is legally guaranteed and is found frequently in the papyri of the settlement of a business transaction. Paul has a parallel thought

"For whatever was written in earlier times was written for our instruction, so that through perseverance and the encouragement of the Scriptures we might have hope." (see note Romans 15:4).

Morris summarizes this section writing that...

As sure as Peter was of what he had seen and heard, this was only his own experience and could only be given as a personal testimony to others. Thus, he stressed that God's written Word, available to all in the holy Scriptures, was more sure than any personal experience he or others might have. It is not in Peter or Paul as men, no matter how sincere or holy they may be, that we must trust, but in Christ as revealed (not in our experience, either) in God's written Word. (Morris, Henry: Defenders Study Bible. World Publishing)

Click for an in depth analysis of the translation/interpretation of this verse.

TO WHICH YOU DO WELL TO PAY ATTENTION: o kalos poieite (2 PPAI) prosechontes (PAPMPN):

“You do well” was a common way of suggesting that a person do something (i.e., “You ought to do this”).

Peter is saying that this is the appropriate attitude a believer should have to the prophetic word. He desires their continued study of Scripture as the safeguard against errors of the false teachers in chapter 2.

To pay attention (4337) (prosecho from pros = toward + echo = have or hold) means to hold the mind or the ear toward something and so to pay attention.

In non-biblical writings the primary meaning of prosecho was to "have in close proximity to"  especially referring to mental processes as in the saying ‘turn one’s mind to.’  Such a person would be in a state of alert.

Prosecho was also a nautical term meaning to hold a ship in a direction, to sail towards. Thus Peter is saying in a sense to hold your course toward your final destination. To keep holding your mind like a lamp in a dark stormy night on the glimmer of the distant lighthouse which keeps the ship on course so that it doesn't crash. Peter was warning believers that since they would be exposed to false teachers, they must pay careful attention to Scripture.

In today’s experience oriented society many people, including Christians, seek to determine truth by the way God has worked in their own lives. But for Peter the splendor of his experience of the transfiguration faded as he spoke of the surety of the written revelation of the prophets. It is an amazing assessment of the validity of holy Scripture that Peter declares it to be more dependable than a voice from heaven heard with the natural ear.

As an aside, if you have never studied the Bible inductively or you are uncertain of the meaning of inductive study, you might take a moment and read the overview tutorial entitled Inductive Bible Study.

Peter was saying you will do well if you make it a habit (present tense = lifestyle) to keep before your mind the living and active Word of Truth which in the context of this letter would expose the error of false teachers.

AS TO A LAMP SHINING: os luchno phainonti (PAPMSD): (The following are some great cross references. Hold your pointer over each or click to read in context. They will make you want to bless the LORD from the depths of your soul - Isa 9:2; 60:1,2; Mt 4:16; Lu 1:78,79; Jn 1:7-8;9 5:35; 8:12; Ep 5:7,8)

Thy word is a lamp to my feet, And a light to my path. (Ps 119:105)

For the commandment is a lamp, and the teaching is light; and reproofs for discipline are the way of life, (Pr 6:23)

Lamp (3088) (luchnos) referred to a portable lamp fed with oil, not a candle, and which was usually placed on a stand in the house.

Shining (5316) (phaino) means to illuminate, give light, shine forth as a luminous body. Shining is present tense (continuous action) which pictures the OT prophetic "lamp" as still shedding its light. The lamp that is shining brightly is the Old Testament, which in the NT is usually indicated by the term "Scriptures".  (Click all 52 uses of the term "Scriptures "used as a synonym of a part or all of the Old Testament)

IN A DARK PLACE: en auchmero topo: (cf Torrey's parallel topic "Spiritual Blindness")

Place (5117) (topos)  means an area of any size (space, place, room), a defined place, the present use being in a geographical or topographical sense, such as a place, a part of a country or even the entire world. Peter combines this word with the adjective below to describe the murky darkness of the fallen world which obscures the truth until the lamp of divine revelation shines forth.

Dark (850) (auchmeros from auchmós = drought produced by excessive heat, dust as in a place where water is evaporated by drought) means dry, without rain parched. The idea is obscure or murky (murky = characterized by a heavy dimness or obscurity caused by or like that caused by overhanging fog or smoke), dismal, dark, squalid (squalid = marked by filthiness and degradation from neglect or poverty and implies sordidness as well as baseness and dirtiness).

Auchmeros pertains to being not only dark, but also dirty and miserable

Auchmeros is used only here in the NT and is not found in the Septuagint (LXX).

Auchmeros does not imply absolute darkness, but that which is dingy, dirty, dusty and filthy as a result of neglect. Dirty things are things devoid of brightness. The light of the (prophetic) lamp exposes the squalid state of the spiritually dark world.

The New Testament writers records that...

the light shines in the darkness, and the darkness did not comprehend (or overcome) it. (John 1:5)

"And this is the judgment, that the light is come into the world, and men loved the darkness rather than the light; for their deeds were evil. For everyone who does evil hates the light, and does not come to the light, lest his deeds should be exposed. But he who practices the truth comes to the light, that his deeds may be manifested as having been wrought in God." (John 3:19-21)

(Jesus instructed Paul to take the Word of the Gospel to the Gentiles) "to open their eyes so that they may turn from darkness to light and from the dominion of Satan to God, in order that they may receive forgiveness of sins and an inheritance among those who have been sanctified by faith in Me." (Acts 26:18)

(Paul explained to the Colossians that the Gospel of Jesus Christ, the Living Word) "delivered us from the domain (authority and power) of darkness, and transferred us to the kingdom of His beloved Son," (see note Colossians 1:13)

Peter does not specifically identify the "dark place" and commentators have advanced several interpretations. It seems most natural however to view this dark place as the world as it presently exists.

The NT frequently refers to the present darkness of this world as shown in these passages...

(Paul explains that) our struggle is not against flesh and blood, but against the rulers, against the powers, against the world forces of this darkness, against the spiritual forces of wickedness in the heavenly places. (Eph 6:12)

(Paul explains to the saints at Thessalonica that) "you, brethren, are not in darkness, that the day should overtake you like a thief; for you are all sons of light and sons of day. We are not of night nor of darkness" (1Th 5:4ff)

(John explains that) On the other hand, I am writing a new commandment to you, which is true in Him and in you, because the darkness is passing away, and the true light is already shining. (1Jn 2:8)

To summarize, Peter is almost certainly using "dark place" as a metaphor to describe this corrupt world system. However "advanced" our secular civilization becomes, this world in its willful rebellion to God (Whose essence is Light), lies in the darkness of sin, ignorance, despair and death which keeps people from seeing God's truth until His light shines into their hearts.

Wiersbe adds that the Greek word auchmeros...

"is the picture of a dank cellar or a dismal swamp. Human history began in a lovely Garden, but that Garden today is a murky swamp. What you see when you look at this world system is an indication of the spiritual condition of your heart. We still see beauty in God’s creation, but we see no beauty in what mankind is doing with God’s creation. Peter did not see this world as a Garden of Eden, nor should we."

UNTIL THE DAY DAWNS: eos ou hemera diaugase (3SAAS):

Dawns (1306) (diaugazo from diá = through + augázo = shine)  means literally to shine through. This word was used to describe daylight breaking through the darkness of night, picturing the first gleams of the sun piercing the darkness.

The day Peter is referring to here is when Christ returns in glory to establish His 1000 Messianic Kingdom. (See notes on The Millennium 1, The Millennium 2, The Millennium 3)

Vincent adds that

 "the verb (diaugazo) is compounded of dia = through, and auge = sunlight, thus carrying the picture of light breaking through the gloom."

Diligent use of the prophetic lamp will be needed only until the day dawns. The word "until" indicates that we are now in the period of waiting, at the end of which prophecy upon its fulfillment will pass away as taught by Paul (1Cor13:8). In other words, the truths in the Bible will continue to point to the source of all truth, Christ, until He returns in glory (At His Second Coming recorded in Revelation  19:13 John records that Christ is "clothed with a robe dipped in blood; and His name is called The Word of God.")

AND THE MORNING STAR ARISES N YOUR HEARTS: kai phosphoros anateile (3SAAS)  en tais kardiais humon:

Morning Star (KJV = Day-star) (5459) (phophoros from phos = light + phero = to bring; English = phosphorus = a substance that glows in the dark) means light bringing, light bearer or bringer or bringing morning light.

 The Latin Vulgate translates "phosphoros" with the word "Lucifer". 

The day-star or morning-star was the name that Greeks assigned to the planet Venus which was the brightest object in the sky apart from the sun and moon and appeared sometimes as the evening star and sometimes as the morning star. In the desert the morning star is so brilliant that it appears as though the sun were about to rise.

Vine adds that phosphoros

 is used of the morning star, as the light–bringer, 2 Pet. 1:19, where it indicates the arising of the light of Christ as the Personal fulfilment, in the hearts of believers, of the prophetic Scriptures concerning His Coming to receive them to Himself. (Vine, W E: Vine's Complete Expository Dictionary of Old and New Testament Words. 1996. Nelson)

In the context these images (day dawning and morning star arising) point to the parousia or the appearing of Jesus Christ.

Consider the following parallel passages...

Because of the tender mercy of our God, with which the Sunrise (KJV = Dayspring = Messiah) from on high shall visit us, TO SHINE UPON THOSE WHO SIT IN DARKNESS AND THE SHADOW OF DEATH, to guide our feet into the way of peace." ( Lu 1:78) (Comment: This was partially fulfilled at Messiah's first coming but will be fulfilled at His return, His light driving away the spiritual darkness of this present evil age)

"I, Jesus, have sent My angel to testify to you these things for the churches. I am the root and the offspring of David, the bright morning star." (Rev 22:16).(Comment: Many evangelical commentators feel that Isaiah 14:12 is a reference to Satan. In that verse the Hebrew and the Greek Septuagint  (Hebrew = heylel = Strong's # 1966 ; LXX translates it with the Greek word heosphoros = bringer of morn, the morning star) are translated Lucifer meaning "light bearer" who represents the counterfeit morning star. Here in the Revelation 22:16, Christ triumphantly proclaims that He is the true "Morning Star". And so we see the final conquest of the counterfeit, the serpent of old, just as was prophesied in the promise in Genesis 3:15 where Moses recorded that the Seed of the woman would crush the head of the serpent. Hallelujah!)

and then (at the end of the Great Tribulation) the sign of the Son of Man (the sign = the glory of Christ) will appear in the sky, and then all the tribes of the earth will mourn, and they will see the SON OF MAN COMING ON THE CLOUDS OF THE SKY with power and great glory (the fulfillment of the Shekinah glory described in Genesis) (Mt 24:30)

(Jesus declares that to those who overcome = those who believe as shown by 1John 5:4-5) 'I will give him the morning star" (Revelation 2:28) (Comment: Christ will give His Own presence to His people, cf 1Thes 4:16-17)

Much as a lamp at night anticipates and is outshined by the bright morning star, so Old Testament prophecy looks ahead to the coming of Christ “the bright Morning Star” Who will outshine all things.

Christians today have the light of Christ within their hearts. At Christ's Second Coming, He will bring all believers into a perfect day. His outward coming will bring light to all people. On this day, the spirits of the godly will take on “an illuminating transformation” as the light of Christ fills them.

Arises  (393) (anatello from aná = up + téllo = set out for a goal) means to cause to arise, spring up, be up. It was used especially of things in natural creation, like the rising of the sun or moon.

Hearts  (2588) (kardia)  (Click in depth study of kardia) is not used to refer literally to the physical heart in the NT but describes the seat of the desires, feelings, affections, passions, impulses. Kardia refers to the causative source of a person’s psychological life in its various aspects, and with special emphasis upon thoughts—‘heart, inner self, mind.'

"Heart" refers to the  the volition (your will), the mind, the desires, etc., though the facility of the intellect may be slightly more emphasized in Scripture. In Hebraic thought the heart is the center of intellectual activity. 

John MacArthur comments on kardia noting that...

Throughout Scripture, as well as in many languages and cultures throughout the world, the heart is used metaphorically to represent the inner person, the seat of motives and attitudes, the center of personality. But in Scripture it represents much more than emotion, feelings. It also includes the thinking process and particularly the will. In Proverbs we are told, “As [a man] thinketh in his heart, so is he” (Pr 23:7, KJV). Jesus asked a group of scribes, “Why are you thinking evil in your hearts?” (Mt 9:4; cf. Mk 2:8; 7:21)... The heart is the control center of mind and will as well as emotion...The problem that caused God to destroy the earth in the Flood was a heart problem. “Then the Lord saw that the wickedness of man was great on the earth, and that every intent of the thoughts of his heart was only evil continually” (Gen. 6:5)....God has always been concerned above all else with the inside of man, with the condition of his heart." ( MacArthur, J: Matthew 1-7 Chicago: Moody Press)

The second coming of Christ will have not only an externally transforming impact on the universe (See notes on 2 Peter 3:7-8, 3:9, 10, 11-13), but also an internally transforming impact (in your hearts) on those believers who are alive when Jesus returns, forever removing any of their remaining doubts. The perfect, albeit limited, revelation of the Scriptures will be replaced with the perfect and complete revelation of Jesus Christ at the second coming (Jn 14:7-11; 21:25). Then the Scriptures will have been fulfilled and believers, will be made like Christ, John recording this encouraging truth...

Beloved, now we are children of God, and it has not appeared as yet what we shall be. We know that, when He appears, we shall be like Him, because we shall see Him just as He is. And everyone who has this hope fixed on Him purifies himself, just as He is pure. (1Jn 3:1,2)

At that time believers will have perfect knowledge and all prophecy will be abolished

"for now we see in a mirror dimly, but then face to face; now (we) know in part, but then (we) will know fully just as (we) also have been fully known." (1Cor 13:14)

Hiebert has an interesting comment on the somewhat difficult to interpret phrase "in your hearts" writing that...

"The truth that Christ is coming again must first arise in their hearts, like the morning star, giving assurance of coming day. Assured of His anticipated return, they will be alert to detect the gleams of dawn breaking through the darkness. Those who disregard the light of prophecy will not understand the significance of these harbingers of coming day. Such a living hope must have a transforming impact upon daily life."