'Unfaithful' in the Bible

But the unfaithful heirs of that kingdom will be thrown into the darkness outside. In that place there will be wailing and gnashing of teeth."

But He replied and said to them, “An evil and adulterous generation [that is morally unfaithful to God] craves and demands a [miraculous] sign; but no sign will be given to it except the sign of the prophet Jonah;

An evil and [morally] unfaithful generation craves a [miraculous] sign; but no sign will be given to it, except the sign of [the prophet] Jonah.” Then He left them and went away.

For whoever is ashamed [here and now] of Me and My words in this adulterous and sinful generation, the Son of Man will also be ashamed of him when He comes in the glory of His Father with the holy angels.”

the master of that servant will come on a day when he doesn't expect him and at an hour that he doesn't know. Then his master will punish him severely and assign him a place with unfaithful people.

What if some of the Jews were unfaithful? Their unfaithfulness cannot cancel God's faithfulness, can it?

Though I am not conscious of having been in any way unfaithful, yet I do not for that reason stand acquitted; but He whose scrutiny I must undergo is the Lord.

if we are unfaithful, he abides faithful, for he cannot deny himself.

You adulteresses [disloyal sinners—flirting with the world and breaking your vow to God]! Do you not know that being the world’s friend [that is, loving the things of the world] is being God’s enemy? So whoever chooses to be a friend of the world makes himself an enemy of God.

But people who are cowardly, unfaithful, detestable, murderers, sexually immoral, sorcerers, idolaters, and all liars will find themselves in the lake that burns with fire and sulfur. This is the second death."