Jami` at-Tirmidhi 1239

Narrated Jabir: "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 to get him and the Prophet (ﷺ) said: 'Sell him to me.' So he purchased him for two black slaves. Then he would not pledge from anyone until he asked him if he was a slave." [He said:] There is something on this topic from Anas. [Abu 'Eisa said:] The Hadith of Jabir is a Hasan Sahih Hadith. This is acted upon according to the people of knowledge. There is no harm in a slave for two slaves in hand to hand exchange, but they differ when it is on credit