God-breathed (YLT)
breathed out by God (ESV)
divinely inspired (Darby)
For the whole Scripture is given by inspiration of God (Geneva)

Scriptures (1124)(see in depth study of graphe)

All (3956) (pas) is an important adjective in this verse as this word includes the idea of oneness, a totality or the whole, thus referring to every passage of Scripture and every word in every passage. No exceptions.

The Net Bible renders the Greek with the phrase every Scripture and then notes that...

There is very little difference in sense between every scripture (emphasizing the individual portions) and “all scripture” (emphasizing the composite whole). The former option is preferred, because it fits the normal use of the word “all/every” in Greek (pas) as well as Paul’s normal sense for the word “scripture” in the singular without the article, as here. So every scripture means “every individual portion of scripture.” (The NET Bible. Biblical Studies Press)

Note that the 1901 Authorized Standard Version (ASV) as well as some other versions (e.g., the Bible in Basic English = BBE, Douay-Rheims = DRB) reads as follows:

Every scripture inspired of God is also profitable

According to this rendering one might reasonably ask "Well, what about those Scriptures that are not inspired by God?"

While this rendering is grammatically possible, this translation to some degree leaves open the implication that there may be some Scripture not inspired by God, which of course is not true, for if any of the whole is not of God, then which part is it? Thus you can see how the integrity and unity of the whole Scripture is undermined. As an illustration take the human body, no part of which which is not useful in its place, and no part of which can be spared without notable loss of functionality of the entire body. So too all of Scripture is profitable for proper function of our spiritual body. Let me ask you - In your personal Bible study, do you focus all your attention on the NT? If you do you are missing a significant portion of the whole counsel of God's Word. How many conservative churches preach almost entirely out of the New Testament, to the virtual exclusion of the Old Testament? Remember that the Old is the New concealed and the New is the Old revealed. Our goal should be that both the Old and New Testaments would be "comfortably" at home in our heart and mind, for every Word of God is profitable. As an aside, there are excellent Bible study programs dealing with the Old Testament, including Bible Study Fellowship (Genesis and the Life of Moses, both 9 month programs and Precept Ministries International with multiple OT studies (Click here for list of over 150 separate in depth inductive lessons covering a significant portion of the entire OT -- with more to come!).

M F Unger wrote that...

Divine inspiration makes the Bible uniquely the Word of God and not merely a book containing the Word of God, and as such is different from any other book sacred or secular.

John MacArthur has a helpful note

"In addition to the many other specific biblical references to the inspiration and authority of Scripture...it is important to note that similar Greek constructions in other parts of the New Testament argue strongly from a grammatical perspective that all Scripture is inspired is the proper translation. Scripture is the revelation conveyed, inspiration is the means of that conveyance. In the words originally revealed and recorded, all Scripture is God’s inerrant Word."

Francis Schaeffer asks and then answers a pertinent question...

Does inerrancy make a difference? Overwhelmingly; the difference is that with the Bible being what it is, God’s Word and so absolute, God’s objective truth, we do not need to be, and we should not be, caught in the ever-changing fallen cultures which surround us.

Scripture (1124) (graphe from grapho = to write; English = graphite - the lead in a pencil!) (Click all 52 uses)  means first  a writing or thing written, a document. The majority of the NT uses refer to the Old Testament writings, in a general sense of the whole collection when the plural (= Scriptures - Matt. 21:42; 22:29; 26:54; Mk. 12:24; 14:49; Lk. 24:27, 32, 45; Jn. 5:39; Acts 17:2, 11; 18:24, 28; Rom. 15:4; 2Pe 3:16) is used and other times of a particular passage when the singular is used (= the Scripture - Mk. 12:10; 15:28; Lk. 4:21; Jn. 13:18; 19:24, 36f; Acts 1:16; 8:35; Ro 11:2; Jas. 2:8, 23) and is used in such a way that quoting Scripture is understood to be the same as quoting God!

Inspired by God (2315) (theopneustos theopneustos from Theos = God + pneo = to breathe or blow) means divinely breathed or given by inspiration of God.

Every single word of Scripture is God breathed. The rabbis taught  that the Spirit of God rested on and in the prophets and spoke through them so that their words did not come from themselves, but from the very mouth of God which is in accord with Peter's declaration that...

"no (absolute negation = absolutely none - and placed first in the Greek for emphasis) prophecy was ever made by an act of human will (no prophet starts a prophecy by himself because he wanted to - the Scriptures are not the product of human effort), but (on the contrary which presents a strong antithesis to the idea that prophecy originated from the mind & will of men) men (the human instruments who "transcribed" as it were the the Words of God) moved by the Holy Spirit (were continually carried or borne along by the Spirit a beautiful figurative use of the verb Luke uses to describe a sailing vessel being carried along by the wind) spoke from God" (see notes on 2 Peter 1:21)

It is not surprising then that in the OT alone, the human writers refer to their writings as the words of God over 3800 times!

The early church was in entire agreement with this view. As discussed above the ASV rendering of 2Timothy 3:16 (“All Scripture inspired by God is...”) leaves open the possibility that some Scripture is not inspired by Him and ultimately would make the Bible worthless as a reliable guide to divine truth. Who would determine which part of it is inspired by God and which is not? And so we see that the doctrine of the inspiration of Scripture is not optional but is vitally important, and thus not surprisingly is a doctrine Satan has attacked from the beginning asking Eve...

“Indeed, has God said?” [Ge 3:1]

The Scriptures are the voice of God to the soul of man. It is inconceivable that God would give His people a book they could not trust. He is the God of truth (KJV Dt 32:4); Jesus is “the truth” (Jn14:6); and the Holy Spirit is the “Spirit is truth” (1Jn 5:7). Jesus said of the Scriptures,

“Thy Word is truth” (Jn 17:17). “

The greater Presbyterian preacher Donald Grey Barnhouse explained inspiration this way...

Just as the Holy Spirit came upon the womb of Mary, so He came upon the brain of a Moses, a David, an Isaiah, a Paul, a John and the rest of the writers of the divine library. The power of the Highest overshadowed them, therefore that holy thing which was born of their minds is called the Holy Bible, the word of God. The writing of Luke will, of course, have the vocabulary of Luke and the work of Paul will bear the stamp of Paul’s mind. However, this is only in the same manner that the Lord Jesus might have had eyes like his mother’s or hair that was the same color and texture as hers. He did not inherit her sins because the Holy Spirit has come upon her. If we ask, how could this be, the answer is God says so. And the writings of men of the Book did not inherit the errors of their carnal minds because their writings were conceived by the Holy Spirit and born out of their personalities without partaking of their fallen nature. If we ask, how could this be, again the answer is God says so.

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The Bible is relevant because it is revealed. It is always a return to reality.

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Richard DeHaan writes the following devotional that humorously illustrates "divine inspiration":

The story is told about a young boy named Timothy who was planning to give his grandmother a Bible for Christmas. He wanted to write something special on the flyleaf but wasn't sure what to say. So he decided to copy what he had seen in a book his father had received from a friend. Christmas morning came and Grandmother opened her gift. She was not only pleased to receive the Bible, but she was amused by the inscription Timothy had put in it. It read:

"To Grandma, with compliments of the author."

Even though that boy was unaware of it, he had suggested a unique fact about the Bible. It came to us from its Author -- God. Knowing who wrote a book often determines whether we'll pick it up and read it. The Bible, with its divine origin, not only ought to be read, but it demands our respect, our trust, and our obedience. It comes "with compliments of the Author." (RDH)

Your thoughts are here, my God,
Expressed in words divine,
The utterance of heavenly lips
In every sacred line.--Bonar

The Bible is a gift from the Author -- God.

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A T Robertson once quipped that...

The greatest proof that the Bible is inspired is that it has stood so much bad preaching.

Augustine of Hippo said...

Let us therefore yield ourselves and bow to the authority of the Holy Scriptures, which can neither err nor deceive.

In the writing of the Jewish historian Josephus (Contra Apion, i.7) we find a statement that parallels 2Ti 3:16:

“The Scripture of the prophets who were taught according to the inspiration of God."

What the Bible says, God says. The Bible is the final authority, the veritable "Supreme Court" from which there is no appeal. It was on such a basis that Martin Luther took his historic stand. The moment of crisis came on April 18, 1521, at the Diet of Worms, when he was called on by Johann von Eck, Official General of the Archbishop of Trier to renounce his errors. Luther replied,

"Unless I am convinced by testimonies of Scripture or by evident reason-for I believe neither the Pope nor Councils alone, since it is established that they have often erred and contradicted themselves-I am the prisoner of the Scriptures cited by me, and my conscience has been taken captive by the Word of God. Here I stand. I can do no other. God help me. Amen." (Bolding added)

The Greek word for "inspired" describes ships sails filled, being carried along over the seas. Paul says every Scripture is the product of the Spirit’s work. He filled the writers and carried them along producing His Words. And even though God's Word bears the mark or style of the writer’s personality, every Word is the true and sure word of God Himself. Next time you read the Word, stop for a moment and contemplate that the eternal, all knowing and all loving God is speaking to your heart and mind and soul and spirit and be amazed as such condescending mercy and grace.

David affirms divine inspiration writing

"The Spirit of the LORD spoke by me, and His word was on my tongue." (2Sa 23:2)

And Jesus Himself reaffirms that the Spirit spoke through David stating that

"David himself said in the Holy Spirit, 'THE LORD SAID TO MY LORD, "SIT AT MY RIGHT HAND, UNTIL I PUT THINE ENEMIES BENEATH THY FEET." (Quoting from Psalm 110) (Mt 12:36)

The author of  Hebrews directly attributes Scripture to the Spirit of God

"Therefore, just as the Holy Spirit says, "TODAY IF YOU HEAR HIS VOICE." (Heb 3:7)

Clearly, the Spirit of God used men of God to write the Word of God. The Spirit did not erase the natural characteristics of the writers. In fact, God in His providence prepared the writers for the task of writing the Scriptures. Each writer has his own distinctive style and vocabulary. Each book of the Bible grew out of a special set of circumstances. In His preparation of men, in His guiding of history, and in His working through the Spirit, God brought about the miracle of the Scriptures.

The Westminster Confession states that...

The authority of the holy Scripture, for which it ought to be believed, and obeyed, dependeth not upon the testimony of any man, or church; but wholly upon God (who is truth itself) the author thereof: and therefore it is to be received, because it is the Word of God.
Westminster Confession

Wiersbe has a cautionary explanation adding that...

"We must not think of “inspiration” the way the world thinks when it says, “Shakespeare was certainly an inspired writer.” What we mean by biblical inspiration is the supernatural influence of the Holy Spirit on the Bible’s writers, which guaranteed that what they wrote was accurate and trustworthy. Revelation means the communicating of truth to man by God; inspiration has to do with the recording of this communication in a way that is dependable. Whatever the Bible says about itself, man, God, life, death, history, science, and every other subject is true. This does not mean that every statement in the Bible is true, because the Bible records the lies of men and of Satan. But the record is true." (Bolding added)

Hiebert comments that

"inspiration is here not asserted of the authors of Scripture but of the writings themselves. But inspiration was not mechanical. The Holy Spirit did not destroy the personality and individual characteristics of the individual writers but rather so worked through the entire being of the writer that the very words used, although truly the words of the human author, were yet the very words the Spirit intended to be employed to express the divine truths being recorded."

“Men do not reject the Bible because it contradicts itself,
but because it contradicts them.” 

The more you read the Bible, the more you love it; the more you love it, the more you read it. Read the Bible as if God were speaking to you. He is!

Scripture is profitable for teaching (what is right), for reproof (what is not right), for correction (how to get right), and for training in righteousness (how to stay right).

A common phrase used to describe "all Scripture" is that it is characterized by "VERBAL PLENARY INSPIRATION".

Inspiration means that the text of Holy Scripture was "breathed-out" by the Holy Spirit and written down by holy men using their own gifts, words and personal style.

Plenary means that inspiration extends to every part of the Bible. Webster defines "plenary" as "complete in every respect". In simple terms, this word conveys the idea that all the words of Scripture are God’s words.

Verbal means that inspiration extends to the very words of the text. When the Bible speaks, God speaks.

Regarding "verbal plenary inspiration", The Pocket Dictionary of Theological Terms states that...

God is the ultimate author of the Bible in its entirety. That is, God’s superintending work in inspiration extends to the whole Bible and to each part of the Bible. Plenary inspiration guarantees that all that the church has come to affirm as Scripture is both authoritative and helpful for Christian belief and practice. (Grenz, S., Guretzki, D., & Nordling, C. F. Pocket dictionary of theological terms. Page 91 . Downers Grove, Ill.: InterVarsity Press)

How important is a proper understanding
of the truth of this verse for you?

The question of the supreme authority of the Word of God is not just some ethereal debate but is the supreme issue. Until you've decided this issue and honestly answered this questions, you're going to be tossed to and fro. Nothing is "of equal value" with the Word of God. It stands supreme. It is the "Supreme Court" of the Christian faith. Tradition may be likened to a lower court, statements of faith to a higher court, councils to a court of appeal. But the Bible itself is the Supreme Court from which there is and can be no appeal.

AND IS PROFITABLE: kai ophelimos: (Ps 19:7, 8, 9, 10, 11, 119:97-99;119:100-102 Ps 119:103-104 119:130 Mic 2:7; Ac 20:20; 20:27 1Co 12:7; Ep 4:11-12 4:13, 4:14, 4:15, 4:16) 

beneficial (ALT)

useful" (Barclay)

Profitable (5624) (ophelimos) means useful, profitable, serviceable, helpful, beneficial and refers to that which yields advantageous returns or results. It provides something that one needs to attain a certain goal -- in context to be a "man of God". Every Scripture serves to meet the moral and spiritual needs of man. Unfortunately as Charles Colson says “The family Bible is more often used to adorn coffee tables or press flowers than it is to feed souls and discipline lives.”

Ophelimos is used 3 times in the NAS: 1 Timothy; 2 Timothy; Titus

In his first epistle Paul uses ophelimos twice to emphasize the temporal and eternal value of godliness reminding Timothy that..

bodily discipline is only of little profit, but godliness is profitable for all things, since it holds promise for the present life and also for the life to come.  (1Timothy 4:8)

Writing to Titus Paul tells that good deeds are profitable..

This is a trustworthy statement (that being justified by His grace we might be made heirs according to the hope of eternal life); and concerning these things I want you to speak confidently, so that those who have believed God may be careful to engage in good deeds. These things are good and profitable for men. (Titus 3:8)

Just as milk nourishes a baby in ways it does not understand, so God’s Word nourishes us in ways we often do not understand.  No matter how deep our understanding of Scripture may be, we still should be able to affirm with the psalmist,

“As the deer pants for the water brooks, so my soul pants for Thee, O God” My soul thirsts for God, for the living God; When shall I come and appear before God? (Ps 42:1, 42:2).

We should rejoice with Paul that

“we all, with unveiled face beholding as in a mirror the glory of the Lord, are being transformed into the same image from glory to glory, just as from the Lord, the Spirit” (2Cor 3:18)

The profit of Scripture attests to its divine inspiration. Although one might wonder about some of the genealogies or obscure passages, the Spirit-taught mind will realize that there is spiritual nourishment in every word that proceeds from the mouth of God.  

John Calvin wrote that...

We cannot rely on the doctrine of Scripture until we are absolutely convinced that God is its author.
John Calvin

John Wesley on the "profitability" of "The Book":

"I am a creature of a day, passing through life as an arrow through the air. I am a spirit, coming from God, and returning to God: just hovering over the great gulf; a few moments hence, I am no more seen; I drop into an unchangeable eternity! I want to know one thing — the way to heaven; how to land safe on that happy shore. God Himself has condescended to teach the way. He hath written it down in a book. Oh, give me that book! At any price, give me the book of God! I have it: here is knowledge enough for me. Let me be homo unius libri: “A man of one book.” Here, then, I am, far from the busy ways of men. I sit down alone; only God is here. In His presence I open, I read His book; for this end — to find the way to heaven." (John Wesley - The Biblical Illustrator)

FOR TEACHING: pros didaskalian: "teach us what is true" (NLT).

Teaching (1319)  (didaskalía from  didasko from dáo = to know or teach) is either the act of teaching or the thing taught and in this use denotes doctrine or what is taught. Doctrine is from Latin doctrina in turn from doceo = to teach. It refers primarily to that which is taught, not the method of teaching, and doctrine.

Doctrine is emphasized in the Pastoral Epistles (19/21 occurrences of doctrine in the NT are found in Paul’s writings and 15/19 are in the Pastoral Epistles) Doctrine structures our thinking and so determines what and how we believe which in turn is reflected in how we behave.  Too often new converts are throw immediately into some ''work'' instead of placing them in the firm footing of vital Biblical doctrine. Sound doctrine is mandatory in order to structure sound thinking and wise living.  If you are not thinking correctly, you cannot be living correctly. The Bible is our source for knowledge concerning God's revelation in Christ.

J C Ryle said..

Let us receive nothing, believe nothing, follow nothing which is not in the Bible, nor can be proved by the Bible.

Puritan Thomas Watson wrote that...

The Scripture is both the breeder and feeder of grace. How is the convert born, but by “the word of truth”? (James 1:18). How doth he grow, but by “the sincere milk of the Word”? (see note 1 Peter 2:2)

FOR REPROOF: pros elegmon: (2Ti 4:2; Pr 6:23; 15:10;15:31 Jn 3:20; Ep 5:11-12;