Deuteronomy 15:17

15:17 you shall take an awl and pierce a hole through his ear to the door. Then he will become your servant permanently (this applies to your female servant as well).

Deuteronomy 31:27

31:27 for I know about your rebellion and stubbornness. Indeed, even while I have been living among you to this very day, you have rebelled against the Lord; you will be even more rebellious after my death!