Wherein God, willing more abundantly to shew unto the heirs of promise the immutability of his counsel, confirmed it by an oath: That by two immutable things, in which it was impossible for God to lie, we might have a strong consolation, who have fled for refuge to lay hold upon the hope set before us.
The perfect and the absolute and the infinite God cannot become anything else but what He is….
If you remember that, it will help you in the hour of trial. It will help you at the time of death, in the resurrection and in the world to come, to know that all that God ever was, God still is. All that God was and is, God ever will be. His nature and attributes are eternally unchanging. I have preached about the uncreated selfhood of God; I’ll never have to change or edit it in anyway…. I go back over some of my old sermons and articles, and I wonder why I wrote them like that. I could improve them now. But I can’t improve on the statement that God is always the same—He is self-sufficient, self-existent, eternal, omnipresent and immutable. There would be no reason to change that because God changes not. His nature, His attributes, are eternally unchanging. AOGII096, 099
Thank You, Lord, for the strong consolation and hope that is based upon the immutability of Your counsel and the unchangeableness of Your nature. Amen. 
6:17 God wanted His believing people to be absolutely assured that what He promised would come to pass. Actually His bare promise would have been enough, but He wanted to show it to a greater extent than even by a promise. So He added an oath to the promise.
The heirs of promise are all those who by faith are children of faithful Abraham. The promise referred to is the promise of eternal salvation to all who believe on Him. When God made a promise of a seed to Abraham, the promise found its full and ultimate fulfillment in Christ, and all the blessings that flow from union with Christ were therefore included in the promise.
6:18 The believer now has two unchangeable things on which to rely—His word and His oath. It is impossible to imagine anything more secure or certain. God promises to save all who believe on Christ; then He confirms it with an oath. The conclusion is inevitable: the believer is eternally secure.
In the remainder of chapter 6 the writer employs four figures to drive home the utter reliability of the Christian hope: (1) a city of refuge, (2) an anchor, (3) a forerunner, and (4) a High Priest.
First, those who are true believers are pictured as fleeing from this doomed world to the heavenly city of refuge. To encourage them in their flight, God has given them an unfailing hope based upon His word and His oath.
- Because God wanted to make the unchanging nature of his purpose very clear to the heirs of what was promised, he confirmed it with an oath.
Once again we read an argument that leads from the lesser to the greater. The Epistle to the Hebrews is replete with examples of this type of argument. Man, by appealing to God, establishes the truth in a particular matter. How much more significant, by comparison, is the oath God himself swears to confirm the certainty of fulfilling his promises to those who have received them. The message that the author of Hebrews conveys is that man can depend on the utter truthfulness of God.
Actually the oath God swears is superfluous, for God himself is truth. Man because of sin confirms the truth of his words by invoking God’s name, but God does not need to establish the truth. Jesus’ prayer to the Father testifies to this: “Your word is truth” (John 17:17).
Why, then, does God swear an oath? He wants to effectively show the heirs of the promise that they can rely fully on his Word. Accommodating himself to human customs, God swears an oath. He is conscious of man’s weak faith. Therefore, to give man added assurance of the complete reliability of God’s Word, God provides the extra affirmation.
Reading Genesis 22:16–17, we receive the impression that God gave the promise to Abraham, for he is the one who obtains the blessing. “I will surely bless you,” God says to Abraham. But the writer of the Epistle to the Hebrews makes the divine blessing applicable to all believers by calling them heirs of the promise. That means that God’s promise to Abraham transcends the centuries and is in Christ as relevant today as it was in Abraham’s time (Gal. 3:7, 9, 29). The oath God swore to Abraham was meant for us to strengthen us in our faith.
When the author writes, “God wanted to make the unchanging nature of his purpose very clear,” he reminds us that the purpose of God is to make us heirs. Furthermore, according to God’s will, this purpose has been determined in eternity (Eph. 1:4–5, 11). God’s purpose to save the believers in Jesus Christ is firm, unchanging, and inviolable.
No believer ought to doubt God’s will to save him, for God gives him perfect assurance that the nature of God’s purpose is unchanging. The believer, who has eternal security because of this unchanging will of God, can sing Fanny J. Crosby’s hymn:
Blessed assurance, Jesus is mine!
O what a foretaste of glory divine!
Heir of salvation, purchase of God,
Born of His Spirit, washed in His blood.
Hebrews 6:17 teaches that God not only made the promise to believers but also is the guarantor of the promise. God makes the promise of salvation, and at the same time he becomes the intermediary who ensures that the promise is fulfilled. The word intermediary implies that there are two other parties: the one who gives the promise and the one who receives it. Between these two parties stands God as guarantor.
- God did this so that, by two unchangeable things in which it is impossible for God to lie, we who have fled to take hold of the hope offered to us may be greatly encouraged.
The available evidence accumulates, as the author notes. God has given his unchangeable promise and he confirmed this promise with an unchangeable oath. Besides noting these “two unchangeable things,” the writer declares that God cannot lie. These statements have a built-in redundancy, for God by nature is the personification of truth. “God is not a man, that he should lie, nor a son of man, that he should change his mind” (Num. 23:19; see also 1 Sam. 15:29; Ps. 33:11; Isa. 46:10–11; Mal. 3:6; James 1:17).
If then God accommodates himself to man’s custom of swearing an oath to establish the truth, the implication is that when a Christian refuses to accept this oath-confirmed promise of salvation and turns to sin or another religion, he risks being blasphemous. This person intimates that God’s Word cannot be trusted and that God is a perjurer.
But in this verse the writer stresses the positive, for he returns to the use of the first person plural. Says he, “We who have fled to take hold of the hope offered to us may be greatly encouraged.” The author directs his lesson on the unchangeableness of God’s purpose to us who believe the Word of God, and he writes to encourage us in our flight from sin. The words we who have fled are somewhat vague because the writer does not provide specific place names or circumstances. However, the general context indicates that we who believe have escaped the power of willful unbelief and thus we turn to God “to take hold of the hope offered to us.” We are the people who “for refuge to Jesus have fled.”
As true heirs of the promise, we take hold of the hope that God offers us. We have fled as fugitives and cling to the one who offers new life. The author uses a figure of speech by which a single word conveys an entire concept. That is, we must understand that the word hope refers to the one who gives that hope. God himself has provided hope through the promises of his Word. And we whom the author of Hebrews exhorts “to make [our] hope sure” (6:11) are invited to appropriate the hope that God places in full view before us.
Taking hold of hope is not something that we do halfheartedly. On the contrary, we must attain the hope offered to us with the strong encouragement that we receive from God’s Word. In short, God holds out to us hope and at the same time strenuously urges us to accept and appropriate it.
 Tozer, A. W., & Eggert, R. (2015). Tozer on the almighty god: a 365-day devotional. Chicago, IL: Moody Publishers.
 MacDonald, W. (1995). Believer’s Bible Commentary: Old and New Testaments. (A. Farstad, Ed.) (p. 2176). Nashville: Thomas Nelson.
 Kistemaker, S. J., & Hendriksen, W. (1953–2001). Exposition of Hebrews (Vol. 15, pp. 173–175). Grand Rapids: Baker Book House.