Cross reference
Leviticus 25:40
40 But let him be with you as a servant working for payment, till the year of Jubilee;
Exodus 21:2-3
2 If you get a Hebrew servant for money, he is to be your servant for six years, and in the seventh year you are to let him go free without payment.
3 If he comes to you by himself, let him go away by himself: if he is married, let his wife go away with him.