Albert Barnes Commentary Leviticus 25:39-40

"And if thy brother be waxed poor with thee, and sell himself unto thee; thou shalt not make him to serve as a bond-servant. As a hired servant, and as a sojourner, he shall be with thee; he shall serve with thee unto the year of jubilee:" — Leviticus 25:39-40 (ASV)

The law here appears harmoniously to supplement the earlier one in Exodus 21:1-6. It was another check applied periodically to the tyranny of the rich. Compare Jeremiah 34:8-17.