Sayyiduna Wathilah bin al-Asqa' (may Allah be pleased with him) said: We came to the Prophet (peace and blessings be upon him) concerning a man who was a companion of ours, for whom the Fire had become obligatory. He (peace and blessings be upon him) said: "Free a slave on his behalf; Allah Almighty will free, for every limb of it, a limb of his from the Fire."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب القسامة / 16480