Hebrews 3:16

but exhort one another day by day, so long as it is called “today”, lest any one of you be hardened by the deceitfulness of sin.

For we have become partakers of Christ, if we hold the beginning of our confidence firm to the end,

while it is said,

“Today if you will hear his voice,

don’t harden your hearts, as in the rebellion.”

With whom was he displeased forty years? Wasn’t it with those who sinned, whose bodies fell in the wilderness?

To whom did he swear that they wouldn’t enter into his rest, but to those who were disobedient?

We see that they weren’t able to enter in because of unbelief.