Miqsam narrates from Abdullah bin Abbas (may Allah be pleased with them both) that two slaves of al-Ta'if accepted Islam, and he (peace and blessings be upon him) set both of them free; one of them was Abu Bakrah (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجزية / 18842