It is narrated from Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) that a slave came and pledged allegiance to the Messenger of Allah (peace and blessings be upon him) upon his migration. The Prophet (peace and blessings be upon him) did not realize that he was a slave. Meanwhile, his master came to take him back. The Noble Prophet (peace and blessings be upon him) said to him, "Sell this slave to me." Thus, the Prophet (peace and blessings be upon him) bought him in exchange for two black slaves. After that, the Prophet (peace and blessings be upon him) would not take allegiance from anyone until he asked whether the person was a slave.