Hebrews 3:12

3:12 See to it, brothers and sisters, that none of you has an evil, unbelieving heart that forsakes the living God.

Hebrews 3:18-19

3:18 And to whom did he swear they would never enter into his rest, except those who were disobedient? 3:19 So we see that they could not enter because of unbelief.