Therefore, as the Holy Spirit says: “Today, if you will hear His voice, Do not harden your hearts as in the rebellion,
In the day of trial in the wilderness,
Where your fathers tested Me, tried Me,
And saw My works forty years. Therefore I was angry with that generation, And said, ‘They always go astray in their heart, And they have not known My ways.’
So I swore in My wrath, ‘They shall not enter My rest.’
”Beware, brethren, lest there be in any of you an evil heart of unbelief in departing from the living God; but exhort one another daily, while it is called “Today,” lest any of you be hardened through the deceitfulness of sin.
For we have become partakers of Christ if we hold the beginning of our confidence steadfast to the end, while it is said: “Today, if you will hear His voice, Do not harden your hearts as in the rebellion.”
For who, having heard, rebelled? Indeed, was it not all who came out of Egypt, led by Moses?
Now with whom was He angry forty years? Was it not with those who sinned, whose corpses fell in the wilderness?
And to whom did He swear that they would not enter His rest, but to those who did not obey?
So we see that they could not enter in because of unbelief.
Hebrews 3:7-19 NKJV