It is narrated from Sayyiduna Abyad bin Hammal (may Allah be pleased with him) that he accepted Islam while three brothers from Kindah, who had been his slaves in the Jahiliyyah, were in his ownership. He went as a delegate to Sayyiduna Abu Bakr (may Allah be pleased with him), and one of them was with him, serving him. That servant spoke to Sayyiduna Abu Bakr (may Allah be pleased with him) during his caliphate, so Sayyiduna Abu Bakr (may Allah be pleased with him) summoned Sayyiduna Abyad bin Hammal (may Allah be pleased with him) and asked him to free the slave who served him, and to sell him his two brothers who were in Ma'rib in exchange for six non-Arab slaves from the captives of al-Qadisiyyah. Sayyiduna Abyad bin Hammal (may Allah be pleased with him) did so: he freed the one who was with him, and in place of his two brothers took six non-Arab slaves from the captives of al-Qadisiyyah. The narrator said: The reason Sayyiduna Abyad bin Hammal (may Allah be pleased with him) went as a delegate to Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him) was that, after the Messenger of Allah (peace and blessings be upon him) passed away, the officials went back on the agreement that Sayyiduna Abyad bin Hammal had made with the Messenger of Allah (peace and blessings be upon him) for seventy garments. Sayyiduna Abu Bakr (may Allah be pleased with him) upheld it just as the Messenger of Allah (peace and blessings be upon him) had set it, until Sayyiduna Abu Bakr (may Allah be pleased with him) passed away. When Sayyiduna Abu Bakr (may Allah be pleased with him) passed away, this agreement came to an end and the matter reverted to the ordinary sadaqah.
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 803