Jabir (may Allah be pleased with him) reports that a slave came and pledged allegiance to the Messenger of Allah (peace and blessings be upon him) for migration. The Prophet (peace and blessings be upon him) did not know that he was a slave. Meanwhile, his master arrived. The Prophet (peace and blessings be upon him) said: "Sell him to me." Then he bought him by giving two black slaves. After that, the Prophet (peace and blessings be upon him) did not take allegiance from anyone until he asked whether he was a slave. .

Imam Tirmidhi says:
1- The hadith of Jabir (may Allah be pleased with him) is Hasan Sahih Gharib.
2- We know it only from the narration of Abu al-Zubair.
3- There is also a narration in this chapter from Ibn Abbas (may Allah be pleased with them both).