Jeremiah 34:13-14

13“This is what the Lord, the God of Israel, says: I made a covenant with your ancestors when I brought them out of the land of Egypt, out of the place of slavery, saying,

14‘At the end of seven years, each of you must let his fellow Hebrew who sold himself to you go. He may serve you six years, but then you must let him go free from your service.’ But your ancestors did not obey me or pay any attention.