Sayyiduna Malik bin al-Harith (may Allah be pleased with him) narrates that he heard the Prophet (peace and blessings be upon him) say: "Whoever takes an orphan of Muslim parents to share his food and drink until he becomes independent of him, Paradise becomes definitely obligatory for him. And whoever frees a Muslim, (the freed slave) will become his means of rescue from Hell; each limb of (the freed slave) will be an expiation for each limb of (the one who freed him)."
Ahmad and al-Tabarani recorded it; its chain contains a narrator, Ali bin Zayd, whose hadith is hasan (good), though he has been declared weak.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب العتق / 7255