7 Therefore, as the Holy Spirit says:
“Today, if you will hear His voice,
8 Do not harden your hearts as in the rebellion,
In the day of trial in the wilderness,
9 Where your fathers tested Me, tried Me,
And saw My works forty years.
10 Therefore I was angry with that generation,
And said, ‘They always go astray in their heart,
And they have not known My ways.’
11 So I swore in My wrath,
‘They shall not enter My rest.’ ”
12 Beware, 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 “Today,” lest any of you be hardened through the deceitfulness of sin. 14 For we have become partakers of Christ if we hold the beginning of our confidence steadfast to the end, 15 while it is said:
“Today, if you will hear His voice,
Do not harden your hearts as in the rebellion.”
16 For who, having heard, rebelled? Indeed, was it not all who came out of Egypt, led by Moses? 17 Now with whom was He angry forty years? Was it not with those who sinned, whose corpses fell in the wilderness? 18 And to whom did He swear that they would not enter His rest, but to those who did not obey? 19 So we see that they could not enter in because of unbelief.
[The New King James Version (Heb 3:7–19). (1982). Thomas Nelson.]
The context of this passage is clear. The Children of Israel did not enter the promised land until after they wanderd around in the desert for 40 years. All perished in that time except 3 believers (if I remember the number correctly). God swore that the unbelief of those who perished would prevent them from going in, and He kept that promise. Yet when the Psalmist wrote Psalm 95:7d-11, he was not talking primarily about the Children of Israel who were led by Moses and who perished in the desert, he was using them as an example of what happens to people in the psalmist's day who hear the Lord's voice and harden their hearts to what He says like the Children of Israel did under Moses. And when the writer of Hebrews recounts the Psalm and the warning, he reiterates that it is not about the past, but is a warning for then present-day people who hear God's voice -- they should not harden their hearts trough unbelief like the Children of Israel did under Moses. And we can take it a step further and say that today, April 7, 2024, if you will hear His voice, do not harden your hearts through unbelief. Instead, cease from your works, rest all your hope in Christ, and enter His rest. Otherwise you will perish according to the example of unbelief set by the Israelites who perished in the desert under Moses. This passage provides no support whatsoever for believing then later perishing through unbelief.