AND THIS [EXPRESSION], "YET ONCE MORE," DENOTES THE REMOVING OF THOSE THINGS WHICH CAN BE SHAKEN AS OF CREATED THINGS IN ORDER THAT THOSE THINGS WHICH CANNOT BE SHAKEN MAY REMAIN: to de eti hapax deloi (3SPAI) (ten) ton saleuomenon (PPPNPG) metathesin os pepoiemenon (RPPNPG) hina meine (3SAAS) ta me saleuomena (PPPNPN): (Psalms 102:26,27; Ezekiel 21:27; Matthew 24:35; 2Peter 3:10,11; Revelation 11:15; 21:1)

This cataclysmic event will explode the myth that what we can see and touch and handle is real and that unseen things are unreal. When God ends the sifting and shaking process, only that which is real will remain. Those who were occupied with the tangible, visible ritualism of Judaism were clinging to things that could and would be shaken.

Denotes (1213) (deloo from delos = manifest, evident) means to make plain by words and thus to declare. To make manifest to the mind. Deloo is used of indications which lead the mind to conclusions about the origin or character of things. It means to make some matter known that was unknown or not communicated previously. It means to show clearly, to signify, to make manifest, visible, clear, or plain and to make known.  When spoken of things past it means to tell, relate or impart information (as in 1Cor 1:11; Colossians 1:18 [note]). Although deloo is used most often in reference to declarations through articulate language, it is also used often (as in the present verse) of any kind of indirect communication.

When spoken of things future or hidden, deloo means to reveal, show or bring to light.

Deloo is used 28 times in the Septuagint (LXX) (Exod. 6:3; 33:12; Deut. 33:10; Jos. 4:7; 1 Sam. 3:21; 1 Ki. 8:36; 2Chr. 6:27; Est. 2:22; Ps. 25:14; 51:6; 147:20; Isa. 42:9; Jer. 16:21; Dan. 2:5f, 9, 11, 16, 23ff, 28ff, 47; 4:18; 7:16). Here are some uses in the  Septuagint (LXX)

Exodus 6:3 and I appeared to Abraham, Isaac, and Jacob, as God Almighty, but by My name, LORD, I did not make Myself known (deloo) to them.

Exodus 33:12 Then Moses said to the LORD, "See, Thou dost say to me, 'Bring up this people!' But Thou Thyself hast not let me know (deloo) whom Thou wilt send with me. Moreover, Thou hast said, 'I have known you by name, and you have also found favor in My sight.'

Esther 2:22 But the plot became known (deloo) to Mordecai, and he told Queen Esther, and Esther informed the king in Mordecai's name.

Psalm 25:14 The secret of the LORD is for those who fear Him, And He will make them know (deloo) His covenant.

Psalm 51:6 Behold, Thou dost desire truth in the innermost being, And in the hidden part Thou wilt make me know (deloo) wisdom.

Psalm 147:20 He has not dealt thus with any nation and as for His ordinances, they have not known (deloo) them. Praise the LORD!

Isaiah 42:9 "Behold, the former things have come to pass, Now I declare new things; Before they spring forth I proclaim (Lxx = deloo = make them known) them to you."

Daniel 2:25 Then Arioch hurriedly brought Daniel into the king's presence and spoke to him as follows: "I have found a man among the exiles from Judah who can make the interpretation known (deloo) to the king!"

Deloo is used 7 times in the NT...

1 Corinthians 1:11 For I have been informed concerning you, my brethren, by Chloe's people, that there are quarrels among you.

1 Corinthians 3:13 each man's work will become evident; for the day will show it, because it is to be revealed with fire; and the fire itself will test the quality of each man's work.

Colossians 1:8 (note) and he also informed us of your love in the Spirit.

Hebrews 9:8 (note)  The Holy Spirit is signifying this, that the way into the holy place has not yet been disclosed, while the outer tabernacle is still standing,

Hebrews 12:27 (note) And this expression, "Yet once more," denotes the removing of those things which can be shaken, as of created things, in order that those things which cannot be shaken may remain.

1 Peter 1:11 (note) seeking to know what person or time the Spirit of Christ within them was indicating as He predicted the sufferings of Christ and the glories to follow.

2 Peter 1:14 (note) knowing that the laying aside of my earthly dwelling is imminent, as also our Lord Jesus Christ has made clear (of something divinely communicated) to me.

Removing (3331) (metathesis from metatíthemi = transfer from meta  = implying change + tithemi = put) is literally, the act of transferring from one place to another  and so the removal or taking up or away. And so it can describe a transfer from one place to another, as for example the translation of a person to heaven...

It refers to the act of God transferring to a new basis, this present universe which is under the curse of Adam’s sin, that new basis being a new and perfect universe. John speaks of this in the words “I saw a new heaven and a new earth: for the first heaven and the first earth were passed away” Revelation 21:1 (see note). The universe was created by God, but will be made to pass away, and to be substituted by a new universe which will exist forever. Thus, transitory, perishable things must pass away, in order that the eternal things may appear in their abiding value. The writer is pointing out that the passing away of perishable things only emphasizes the eternal. One of these is mentioned in the next verse, an eternal kingdom, the kingdom of God’s rule over the saved of the human race on a new earth all through eternity. The old earth will pass away and a new earth will be made so that the saints might have a fit place of habitation throughout the eternal ages. (Wuest, K. S. Wuest's Word Studies from the Greek New Testament: Eerdmans or Logos)

C H Spurgeon - Morning and evening : Daily readings (June 22 PM) - We have many things in our possession at the present moment which can be shaken, and it ill becomes a Christian man to set much store by them, for there is nothing stable beneath these rolling skies; change is written upon all things. Yet, we have certain “things which cannot be shaken,” and I invite you this evening to think of them, that if the things which can be shaken should all be taken away, you may derive real comfort from the things that cannot be shaken, which will remain. Whatever your losses have been, or may be, you enjoy present salvation. You are standing at the foot of his cross, trusting alone in the merit of Jesus’ precious blood, and no rise or fall of the markets can interfere with your salvation in him; no breaking of banks, no failures and bankruptcies can touch that. Then you are a child of God this evening. God is your Father. No change of circumstances can ever rob you of that. Although by losses brought to poverty, and stripped bare, you can say, “He is my Father still. In my Father’s house are many mansions; therefore will I not be troubled.” You have another permanent blessing, namely, the love of Jesus Christ. He who is God and Man loves you with all the strength of his affectionate nature—nothing can affect that. The fig tree may not blossom, and the flocks may cease from the field, it matters not to the man who can sing, “My Beloved is mine, and I am his.” Our best portion and richest heritage we cannot lose. Whatever troubles come, let us play the man; let us show that we are not such little children as to be cast down by what may happen in this poor fleeting state of time. Our country is Immanuel’s land, our hope is above the sky, and therefore, calm as the summer’s ocean; we will see the wreck of everything earthborn, and yet rejoice in the God of our salvation. (Spurgeon, C. H.).

THEREFORE SINCE WE RECEIVE A KINGDOM WHICH CANNOT BE SHAKEN LET US  SHOW GRATITUDE BY WHICH WE MAY OFFER TO GOD AN ACCEPTABLE SERVICE WITH REVERENCE) AND AWE: Dio basileian asaleuton paralambanontes (PAPMPN) echomen (1PPAS) charin, di' es latreuomen (1PPAS) euarestos to theo meta eulabeias kai deous:  (Isa 9:7; Da 2:44; 7:14,27; Mt 25:34; Lk 1:33; 17:20,21; 1Pe 1:4,5; Rev 1:6; 5:10) (we may -Ps 19:14; Isa 56:7; Ro 12:1,2; Eph 1:6; 5:10; Php 4:18; 1Pe 2:5,20) (reverence and awe - Heb 4:16; 5:7; 10:19,22; Lev 10:3; Ps 2:11; 89:7; Pr 28:24; Ro 11:20; 1Pe 1:17; Rev 15:4)

Therefore since we receive  - for this cause ~ because of the truth that follows. This truth should give us a motivation and should inspire worshipful service out of a heart filled with thanksgiving at the truth that what we have in Christ can never be moved or shaken no matter what we might be experiencing in the temporal by and by. We today like the original Jewish readers of this letter have a Solid Rock, Who was also a merciful and faithful High Priest, seated forever as our Advocate at the right hand of God.

NKJV is a somewhat more literal rendering than NAS...

Therefore, since we are receiving a kingdom which cannot be shaken, let us have grace (instead of "let us show gratitude"), by which we may serve God acceptably with reverence and godly fear.

Note let us have is in the present tense so it could be paraphrased let us have a lifestyle of grace, one lived continually in His transforming power. Grace is the only way a believer can offer an "acceptable" service to a holy God (deeds done in our own strength are as "filthy rags" Isaiah 64:6). Grace is the only way to we can continually show affection to brethren (Hebrews 13:1) and the only way to not neglect demonstrating affection to strangers (Hebrews 13:2).

Click for all 12 "let us..." exhortations in Hebrews (in the NASB).

Why should we "show gratitude"? Because we have a kingdom which cannot be shaken. This should inspire the most fervent worship and adoration. We should unceasingly praise Him with reverence and godly fear.

Hebrews 2:2 For if the word spoken through angels proved unalterable, and every transgression and disobedience received a just recompense,

Hebrews 3:6 but Christ was faithful as a Son over His house whose house we are, if we hold fast our confidence and the boast of our hope firm until the end.

Hebrews 3:14 For we have become partakers of Christ, if we hold fast the beginning of our assurance firm until the end;

Hebrews 6:19 This hope we have as an anchor of the soul, a hope both sure and steadfast and one which enters within the veil,

Acceptable (2102) (euarestos from euárestos = pleasing, well–pleasing from eu = well + arésko = please) pertains to that which causes someone to be pleased. Pleasingly, acceptably. In an acceptable way, a manner well-pleasing to another.

How can our service be "acceptable" to God? To help understand meaning see root aresko (700) in Romans 8 where Paul writes that...

and those who are in the flesh cannot please (aresko) God. (see note Romans 8:8)

S Lewis Johnson writes that Romans 8:8...

Awe (127) (deos) from Homer down refers to fear or awe and then reverence. It is like an apprehension of danger as when alone in a deep, dark forest. Apprehension due to God's glory and majesty. It is that sense of profound respect and reverence for deity, in this case the living God, His majesty and holy presence.

When the voice and tread of a wild beast are distinctly heard close at hand the deos becomes phobos.

As Ray Stedman (reference) says...

there are some things which cannot be shaken and which will remain forever. That which is shaken and removed is so done in order that what cannot be shaken may stand revealed. Such an unshakable thing is the kingdom of God into which those who trust in Jesus have entered. It is present wherever the King is honored, loved and obeyed. The present active participle (“are receiving”) indicates a continuing process. We enter the kingdom at conversion, but we abide in it daily as we reckon upon the resources which come to us from our invisible but present King. Such unbroken supply should arouse a continuing sense of gratitude within us and lead to acceptable worship of God. What renders such worship acceptable is the sense of God as incredibly powerful and majestic in person, and yet loving and compassionate of heart. An old hymn (play) puts it well:

Immortal, invisible, God only wise,
In light inaccessible, hid from our eyes.
How blessed, how glorious, the Ancient of Days
Almighty, Victorious, thy great name we praise!

Our Daily Bread - Temporary Or Eternal - The Seven Wonders of the Ancient World were wonderful indeed! These impressive creations of human genius include the Tomb of Mausolos, built in 350 bc; the Temple of Artemis at Ephesus; the Hanging Gardens of Babylon; King Ptolemy's lighthouse near Alexandria; the 100-foot statue of Apollo called the Colossus of Rhodes; the 40-foot statue of Zeus in the city of Olympia; and the great pyramids of Egypt.

Six of these remarkable achievements have been destroyed--Ptolemy's lighthouse by an earthquake, and the other five demolished by plunderers. Only the pyramids remain to fill us with awe.

We may marvel over these Seven Wonders, but we must never forget that everything in our world is temporary. I remember looking at the skyline of New York City from the stern of a ferryboat and recalling the lines of a hymn: "These all shall perish, stone on stone; but not Thy kingdom nor Thy throne."

The writer of Hebrews said, "Since we are receiving a kingdom which cannot be shaken, let us . . . serve God acceptably with reverence and godly fear" (Heb 12:28). These words and the words of Psalm 102 help us to keep the temporary and the eternal in perspective. —Vernon C Grounds (Our Daily Bread, Copyright RBC Ministries, Grand Rapids, MI. Reprinted by permission. All rights reserved)

Swift to its close ebbs out life's little day,
Earth's joys grow dim, its glories pass away;
Change and decay in all around I see--
O Thou who changest not, abide with me! --Lyte

Hold tightly to what is eternal and loosely to what is temporal.

Our Daily Bread - Frozen Snowball - Baseball pitcher Tug McGraw had a wonderful philosophy of pitching. He called it his “frozen snowball” theory.“ If I come in to pitch with the bases loaded, ”Tug explained,“ and heavy hitter Willie Stargell is at bat, there’s no reason I want to throw the ball. But eventually I have to pitch. So I remind myself that in a few billion years the earth will become a frozen snowball hurtling through space, and nobody’s going to care what Willie Stargell did with the bases loaded!”

The Bible tells us the earth will someday “melt with fervent heat; both the earth and the works that are in it will be burned up”(2Peter 3:10). Yet McGraw’s point is valid: We need to keep life in perspective. Most of the things we worry about have no eternal significance.

The writer of Hebrews was concerned about our perspective. Throughout the book, he keeps our eyes focused on heaven and away from earth. Unless our minds are on heaven, we will have little eternal influence on earth.

There will come a time when the earth will be shaken, and things that once seemed permanent will be gone (Hebrews 12:27). What you fear most today will be forgotten like yesterday’s headlines. What really matters is what you do today that has a touch of eternity about it.—Haddon W. Robinson (Ibid)

FOR OUR GOD IS A CONSUMING FIRE: kai gar o theos hemon pur katanaliskon. (PAPNSN): (Heb 10:27; Ex 24:17; Nu 11:1; 16:35; Deut 4:24; 9:3; Ps 50:3; 97:3; Isaiah 66:15; Daniel 7:9; 2Th 1:8)

For - term of explanation - Explains why we should have reverence and awe!

Stedman sums up this fifth and final warning writing that...

The proper attitude of Christians must be one of awe that a Being of such majesty and glory could find a way to dwell eternally with such sin controlled and sin-injured creatures as us. Since our “God is a consuming fire,” we must cry with Isaiah, “Who of us can dwell with the consuming fire? Who of us can dwell with everlasting burning?” (Isaiah 33:14). God’s love is just such a fire, it destroys what it cannot purify, but purifies what it cannot destroy. In Jesus we have a relationship that cannot be destroyed (Ro 8:38, 39-note). Our great king is leading us through trials and difficulties in order that we may at last cry with Job, “He knows the way that I take; when he has tried me, I shall come forth as gold” (Job 23:10KJV-note). (Hebrews 12:25-29 Fifth and Final Warning )

Note that katanalisko is in the present tense  which speaks of continuous action. In other words the text says that “our ‘God IS [not was!] a consuming fire.’ The God of Zion is the same God as the God of Sinai. God has not changed. Granted, Christians ought to laugh and in fact in one sense they ought to have the best sense of humor on this planet. And Christians ought to enjoy life but they must also know and understand that God remains a “Consuming fire” and that acceptable worship takes place when there is authentic “reverence and awe.” This is God’s Word! And so when we come to worship, we must keep both mountains in view, the approachable Mt Zion with its consuming love, and the unapproachable Mt Sinai with its consuming fire and then come in reverent boldness.

Our Daily Bread - I'm Afraid Of God - Many times I have talked to people about our need to fear God. I've heard them respond something like this: "You're not really afraid of God, are you? I'd never believe in that kind of God."

Yes, I am afraid of God, and I'm not afraid to admit it. I also fear water. That doesn't mean I don't love to fish and swim. But I never want to forget the life-taking power of a river, a lake, or an ocean.

In a more personal way, I remember as a boy fearing my dad. I loved him and knew he loved me and was concerned for my good. But I respected his authority as my father, and I was afraid of the corrective measures he would take if I did wrong.

The same is true in my relationship with God. I stand in awe of Him and His holiness. And because I do, I love Him and want to be close to Him. I desire to love what He loves and hate what He hates. I want to live with the awareness that He is to be feared more than anyone. Satan and people may destroy the body, but God is "a consuming fire" who can "destroy both soul and body in hell" (Mt. 10:28).

Only as we fear God do we truly love Him. And only as that love grows will it guarantee that our fear of God is the right kind of fear. —Mart De Haan (Our Daily Bread, Copyright RBC Ministries, Grand Rapids, MI. Reprinted by permission. All rights reserved) 

To fear the Lord means giving Him
Our reverence, trust, and awe,
Acknowledging His sovereignty,
Submitting to His law. --Hess

Fear God and you will have nothing else to fear.

Our Daily Bread - He Is A Fire - On December 5, 2002, the headline announced:

Ring Of Fire Encircles Sydney - A firestorm was raging outside the Australian city. Many people feared that this bushfire would prove to be Sydney's worst in decades. Fanned by strong winds, high temperatures, and low humidity, the fire jumped across roads and rivers, consuming everything in its path.

When we think about the destructive power of that kind of inferno, we gain a better understanding of the startling words of Hebrews 12:29, "Our God is a consuming fire."

Why did the author of Hebrews use such graphic imagery to describe the Lord? In his letter he was dealing with spiritual life-and-death issues—what his readers believed and the reality of their faith. Their response would reveal whether they were investing their lives in the kingdom that will last forever, or in the one destined for destruction.

We too need to remember that this world and all we possess are only temporary. If our faith and hope are in Jesus Christ, we are part of a kingdom that cannot be destroyed (v.28). Knowing that our days on earth are numbered and that "our God is a consuming fire," let us serve Him and invest in things that are imperishable.—Albert Lee (Ibid)