Musannaf Ibn Abi Shaybah 39349 — The acceptance of Islam by Abu Bakr

Qays said: Sayyiduna Abu Bakr (may Allah be pleased with him) bought Sayyiduna Bilal (may Allah be pleased with him) for five uqiyahs while he was buried under stones. The polytheists said: If you had been willing to buy him for one uqiyah, we would (still) have sold him to you. Sayyiduna Abu Bakr said: If you had been willing to sell him only for a hundred uqiyahs, I would (still) have bought him.