'Unfaithfulness' in the Bible

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.

All Israel was registered in the genealogies that are written in the Book of the Kings of Israel. But Judah was exiled to Babylon because of their unfaithfulness.

Saul died for his unfaithfulness to the Lord because he did not keep the Lord’s word. He even consulted a medium for guidance,