Jeremiah 34:14-15
34:14 “Every seven years each of you must free any fellow Hebrews who have sold themselves to you. After they have served you for six years, you shall set them free.” But your ancestors did not obey me or pay any attention to me.
34:15 Recently, however, you yourselves showed a change of heart and did what is pleasing to me. You granted your fellow countrymen their freedom and you made a covenant to that effect in my presence in the house that I have claimed for my own.