Jeremiah 34:13-14

13"Thus says the Lord, the God of Israel: I myself made a covenant with your fathers when I brought them out of the land of Egypt, out of the house of slavery, saying,

14'At the end of seven years each of you must set free the fellow Hebrew who has been sold to you and has served you six years; you must set him free from your service.' But your fathers did not listen to me or incline their ears to me.