'Unfaithfulness' in the Bible

then I shall set My face against that man and against his [extended] family, and I will cut off from their people both him and all who follow him in playing the prostitute (commit apostasy) with Molech.

But they acted treacherously against the God of their fathers and played the prostitute with the gods of the peoples of the land, whom God had destroyed before them.

So all Israel was enrolled by genealogies; and they are written in the Book of the Kings of Israel. And Judah was carried away into exile to Babylon because of their unfaithfulness [to God].

So Saul died for his trespass which he committed against the Lord, for his failure to keep the word of the Lord; and also because he consulted a medium [regarding a spirit of the dead], to inquire of her,

His prayer also and how God heard him, and all his sin, his unfaithfulness, and the sites on which he built high places and set up the Asherim and the carved images, before he humbled himself, behold, they are written in the records of the Hozai.

Remove from me the way of falsehood and unfaithfulness,And graciously grant me Your law.

“Upon a high and lofty mountainYou have [openly and shamelessly] made your [idolatrous and adulterous] bed;Even there you went up to offer sacrifice [to idols, in spiritual unfaithfulness to Me].

“Lift up your eyes to the barren heights and see;Where have you not been violated?You sat by the road waiting [eagerly] for them [those man-made gods]Like an Arab [tribesman who waits to attack] in the desert,And you have desecrated the landWith your [vile] prostitution and your wickedness (disobedience to God).

They will forget their disgrace and all their treachery (unfaithfulness) which they perpetuated against Me, when they live securely in their own land and there is no one who makes them afraid.

but I say to you that whoever divorces his wife, except on grounds of sexual immorality, causes her to commit adultery; and whoever marries a woman who has been divorced commits adultery.