Leviticus 25:42-46

⁴²For they are my servants whom I took out from the land of Egypt; they may not become the property of another.

⁴³Do not be a hard master to him, but have the fear of God before you.

⁴⁴But you may get servants as property from among the nations round about; from them you may take men-servants and women-servants.

⁴⁵And in addition, you may get, for money, servants from among the children of other nations who are living with you, and from their families which have come to birth in your land; and these will be your property.

⁴⁶And they will be your children's heritage after you, to keep as their property; they will be your servants for ever; but you may not be hard masters to your countrymen, the children of Israel.