"A slave came to give the pledge to the Prophet (ﷺ) for Hijrah, but the Prophet (ﷺ) did not realize that he was a slave. So his master came, and the Prophet (ﷺ) said: 'Sell him to me.' So he purchased him for two black slaves. After this he (ﷺ) would not take the pledge from anyone until he asked him if he was a slave."

There is something on this topic from Ibn 'Abbas.

The Hadith of Jabir is Hasan Gharib Sahih, we do not know of it except as a narration of Abu Az-Zubair.

Jami` at-Tirmidhi Book 21, Hadith 58