'Unbelief' in the Bible

So we see that they were not able to enter [into His rest—the promised land] because of unbelief and an unwillingness to trust in God.

Let us therefore make every effort to enter that rest [of God, to know and experience it for ourselves], so that no one will fall by following the same example of disobedience [as those who died in the wilderness].

By faith [with confidence in God and His word] Noah, being warned by God about events not yet seen, in reverence prepared an ark for the salvation of his family. By this [act of obedience] he condemned the world and became an heir of the righteousness which comes by faith.