I wasn't saying that the first sentence of Hebrews doesn't make sense, but that I can't understand why it is in the text if it functions as a prologue without serving any other meaningful purpose pertaining to the thematic development of the book.
The same probation for Israel as the people of God, the Hebrews, meaning 40 years while the old folks who would not accept Christ died off, is happening for the actual event of entering into the "rest" of God, equals salvation from their own works, that the wilderness wandering typified. It is brought to bear on the theme.
Heb 3:7 Wherefore (as the Holy Ghost saith, To day if ye will hear his voice,
8 Harden not your hearts, as in the provocation, in the day of temptation in the wilderness:
9 When your fathers tempted me, proved me, and saw my works forty years.
10 Wherefore I was grieved with that generation, and said, They do alway err in their heart; and they have not known my ways.
11 So I sware in my wrath, They shall not enter into my rest.)
12 Take heed, brethren, lest there be in any of you an evil heart of unbelief, in departing from the living God.
13 But exhort one another daily, while it is called To day; lest any of you be hardened through the deceitfulness of sin.
14 For we are made partakers of Christ, if we hold the beginning of our confidence stedfast unto the end;
15 While it is said, To day if ye will hear his voice, harden not your hearts, as in the provocation.
16 For some, when they had heard, did provoke: howbeit not all that came out of Egypt by Moses.
17 But with whom was he grieved forty years? was it not with them that had sinned, whose carcases fell in the wilderness?
18 And to whom sware he that they should not enter into his rest, but to them that believed not?
19 So we see that they could not enter in because of unbelief.
This is not the end of the story. There is a therefore to begin the next chapter that completes the reason for saying what I have quoted.
It was 40 years between the resurrection of Jesus Christ and the dispersion of Judah out of Palestine in total. They are reckoned dead as a nation at that time, and time for them stopped because time does not go on for a dead person or a dead nation.
The admonition of this letter is to not go back to the weak and beggarly elements of the law of Moses after having been enlightened during these years by the Holy Ghost and the preaching of the apostles. It was written in 66 AD. The end, or the dispersion, was in 70 AD. If these Jews would have trusted Christ during these years as a nation, then all the OT prophesies would have taken place and Jesus Christ would have come in his revelation. However they did not take heed as per V 12 above.
Heb 6:4 For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost,
5 And have tasted the good word of God, and the powers of the world to come,
6 If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame.
7 For the earth which drinketh in the rain that cometh oft upon it, and bringeth forth herbs meet for them by whom it is dressed, receiveth blessing from God:
8 But that which beareth thorns and briers is rejected, and is nigh unto cursing; whose end is to be burned.
9 But, beloved, we are persuaded better things of you, and things that accompany salvation, though we thus speak.
He 10:15 Whereof the Holy Ghost also is a witness to us: for after that he had said before,
16 This is the covenant that I will make with them after those days (of the law of Moses), saith the Lord, I will put my laws into their hearts, and in their minds will I write them;
17 And their sins and iniquities will I remember no more.
18 Now where remission of these is, there is no more offering for sin.
19 Having therefore, brethren, boldness to enter into the holiest by the blood of Jesus,
20 By a new and living way, which he hath consecrated for us, through the veil, that is to say, his flesh;
21 And having an high priest over the house of God;
22 Let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience, and our bodies washed with pure water.
23 Let us hold fast the profession of our faith without wavering; (for he is faithful that promised
24 And let us consider one another to provoke unto love and to good works:
25 Not forsaking the assembling of ourselves together, as the manner of some is; but exhorting one another: and so much the more, as ye see the day approaching.
26 For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins,
27 But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries.
28 He that despised Moses' law died without mercy under two or three witnesses:
29 Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done despite unto the Spirit of grace?
30 For we know him that hath said, Vengeance belongeth unto me, I will recompense, saith the Lord. And again, The Lord shall judge his people.
31 It is a fearful thing to fall into the hands of the living God.
32 But call to remembrance the former days, in which, after ye were illuminated, ye endured a great fight of afflictions;
33 Partly, whilst ye were made a gazingstock both by reproaches and afflictions; and partly, whilst ye became companions of them that were so used.
34 For ye had compassion of me in my bonds, and took joyfully the spoiling of your goods, knowing in yourselves that ye have in heaven a better and an enduring substance.
35
Cast not away therefore your confidence, which hath great recompence of reward.
36 For ye have need of patience, that, after ye have done the will of God, ye might receive the promise.
37 For yet a little while, and he that shall come will come, and will not tarry.
38 Now the just shall live by faith:
but if any man draw back, my soul shall have no pleasure in him.
39 But we are not of them who draw back unto perdition; but of them that believe to the saving of the soul.
This probably will not make much sense to you having not learned the special relationship between God and the Hebrews and how he is working salvation for the world through them.
This people remains a nation with the covenant promises when this letter was written. There are 7 years left for this nation to be purified in the future.
