'Believing' in the Bible

for, seeing in the wisdom of God the world through the wisdom knew not God, it did please God through the foolishness of the preaching to save those believing.

If anyone destroys the temple of God [corrupting it with false doctrine], God will destroy the destroyer; for the temple of God is holy (sacred), and that is what you are.

For the unbelieving husband is sanctified through his wife, and the unbelieving wife is sanctified through her believing husband; for otherwise your children are unclean, but now they are holy.

We have the right to take a believing wife with us like the other apostles, the Lord's brothers, and Cephas, don't we?

so that the tongues are for a sign, not to the believing, but to the unbelieving; and the prophesy is not for the unbelieving, but for the believing,

Yes, even those who have died believing in the Messiah are lost.