Hebrews 3:10-11, 17-19

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.’ ”

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.