Sayyiduna Samurah bin Jundub (may Allah be pleased with him) narrated from the Prophet (peace and blessings be upon him) that he (peace and blessings be upon him) said: "Whoever kills his slave, we will kill him; and whoever cuts off a limb of his, we will cut off his limb." Qatadah (may Allah have mercy on him) said: Then al-Hasan (may Allah have mercy on him) forgot this hadith and began to say: A free man is not to be killed for a slave. Al-Shaykh (may Allah have mercy on him) said: It is possible that al-Hasan (may Allah have mercy on him) did not forget it, but rather abandoned it because of its weakness. Most of the scholars of hadith turned away from al-Hasan's narrations from Samurah (may Allah be pleased with him), and some of them held that al-Hasan (may Allah have mercy on him) did not hear any hadith from Samurah (may Allah be pleased with him) except the hadith of the aqiqah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15946