Jeremiah 34:13-14

13“Thus says the Lord, the God of Israel: ‘I made a covenant with your fathers in the day that I brought them out of the land of Egypt, out of the house of bondage, saying,

14“At the end of seven years let every man set free his Hebrew brother, who has been sold to him; and when he has served you six years, you shall let him go free from you.” But your fathers did not obey Me nor incline their ear.