Sayyiduna Abu Dharr al-Ghifari (may Allah be pleased with him) narrates: I heard the Prophet (peace and blessings be upon him) say: "Whoever frees a believing neck (that is, a slave), this flows through each of his limbs (the narrator is unsure; perhaps the words are:) it frees each of his limbs from Hell."
Al-Bazzar recorded it; its chain contains a narrator, Abu Hariz, whom Ibn Hibban and, according to one report, Yahya bin Ma'in declared thiqah (trustworthy), while the majority of the imams declared him da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب العتق / 7257