It is narrated from Hazrat Uqbah bin Amir (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: Whoever frees a Muslim slave, it will become a means of freedom from Hell for him.
Hadith Referenceمسند احمد / مسند الشاميين / 17326
Hadith Gradingحکم دارالسلام:صحيح لغيره، وهذا إسناد ضعيف لانقطاعه، قتادة لم يلق قيساً الجذامي