Charles Ellicott Commentary Exodus 12:44

"but every man`s servant that is bought for money, when thou hast circumcised him, then shall he eat thereof." — Exodus 12:44 (ASV)

Every man’s servant. —Slaves born in the house were required to be circumcised on the eighth day, like Israelites (Genesis 17:13). Bought slaves were allowed their choice. It is noticeable that the circumcised slave was to be admitted to full religious equality with his master.