Jami` at-Tirmidhi, Volume 3, Book 12, Hadith 1239 (DarusSalam) ⓘ

Narrated Jabir: "A slave came to give the pledge to the Prophet for Hijrah, but the Prophet did not realize that he was a slave. So his master came to get him and the Prophet 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.

حَدَّثَنَا قُتَيْبَةُ، أَخْبَرَنَا اللَّيْثُ، عَنْ أَبِي الزُّبَيْرِ، عَنْ جَابِرٍ، قَالَ جَاءَ عَبْدٌ فَبَايَعَ النَّبِيَّ صلى الله عليه وسلم عَلَى الْهِجْرَةِ وَلاَ يَشْعُرُ النَّبِيُّ صلى الله عليه وسلم أَنَّهُ عَبْدٌ فَجَاءَ سَيِّدُهُ يُرِيدُهُ فَقَالَ النَّبِيُّ صلى الله عليه وسلم ‏ "‏ بِعْنِيهِ ‏" ‏ ‏.‏ فَاشْتَرَاهُ بِعَبْدَيْنِ أَسْوَدَيْنِ ثُمَّ لَمْ يُبَايِعْ أَحَدًا بَعْدُ حَتَّى يَسْأَلَهُ أَعَبْدٌ هُوَ قَالَ وَفِي الْبَابِ عَنْ أَنَسٍ ‏.‏ قَالَ أَبُو عِيسَى حَدِيثُ جَابِرٍ حَدِيثٌ حَسَنٌ صَحِيحٌ ‏.‏ وَالْعَمَلُ عَلَى هَذَا عِنْدَ أَهْلِ الْعِلْمِ أَنَّهُ لاَ بَأْسَ بِعَبْدٍ بِعَبْدَيْنِ يَدًا بِيَدٍ ‏.‏ وَاخْتَلَفُوا فِيهِ إِذَا كَانَ نَسِيئًا ‏.‏