Deuteronomy 15:15

15:15 Remember that you were a slave in the land of Egypt and the Lord your God redeemed you; therefore, I am commanding you to do this thing today.

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 24:18

24:18 Remember that you were slaves in Egypt and that the Lord your God redeemed you from there; therefore I am commanding you to do all this.

Deuteronomy 24:22

24:22 Remember that you were slaves in the land of Egypt; therefore, I am commanding you to do all this.