Jeremiah 3:20
Surely as a wife treacherously departeth from her husband, so have ye dealt treacherously with me, O house of Israel, saith the LORD. Surely as a wife treacherously departeth from her husband, so have ye dealt treacherously with me, O house of Israel, saith the LORD.
Israel's dealing with God is as a wife treacherously departing from her husband, breaking her marriage vow and breaking faith with him. The marriage figure means that God had bound His people to Himself, holding them to Himself by a covenant bond. Their turning away from Him was spiritual unfaithfulness, a treacherous departure from the Lord to whom they belonged.
That treachery consisted in turning trust and affection away from God to other objects, giving their confidence and affection elsewhere instead of to Him. Specifically it was turning that confidence and affection toward worldly things. At the same time the comparison displays the love and faithfulness of God toward Israel, a love and faithfulness which Israel despised.