Sayyiduna Wathilah bin al-Asqa' (may Allah be pleased with him) said: We went out with the Messenger of Allah (peace and blessings be upon him) on the expedition of Tabuk, and some people of Banu Sulaym came and said: "O Messenger of Allah, a companion of ours has made the Fire obligatory upon himself." He (peace and blessings be upon him) said: "Let a slave be freed on his behalf; Allah will free, for every limb of it, a limb of his from the Fire."
Hadith Referenceالمعجم الكبير للطبراني / باب الواو / 18440