Charles Spurgeon Commentary Deuteronomy 15:12

"If thy brother, a Hebrew man, or a Hebrew woman, be sold unto thee, and serve thee six years; then in the seventh year thou shalt let him go free from thee." — Deuteronomy 15:12 (ASV)

He might be under an apprenticeship of servitude for six years; but the seventh year was to be a year of rest to him, as it was a year of release to debtors, and of rest to the land.