Deuteronomy 15:15-17

15Remember that you were slaves in Egypt and the LORD your God redeemed you. That is why I give you this command today. 16But if your servant says to you, “I do not want to leave you,” because he loves you and your family and is well off with you,

17then take an awl and push it through his earlobe into the door, and he will become your servant for life. Do the same for your female servant.