1 Bible Verses about Apostasy in OT

while it is said, To-day if ye will hear his voice, harden not your hearts as in the provocation. For some, though they had heard, provoked him; yet not all who came out of Egypt by Moses. But against whom was he incensed forty years? Was it not against those who had sinned, whose corpses fell in the wilderness?read more.
And to whom did he swear that they should not enter into his rest, but to those who did not believe? So we see that they could not enter in because of unbelief.