He who sets free a Muslim slave, Allah will deliver from the fire of Hell every part of his body in return for every part of the slave's body, even his private parts
Authentic hadithعن أبي هريرة رضي الله عنه مرفوعاً: «من أعتق رقبة مسلمة أعتق الله بكل عضو منه، عضوًا منه في النار، حتى فرجه بفرجه».
Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "He who sets free a Muslim slave, Allah will deliver from the fire of Hell every part of his body in return for every part of the slave's body, even his private parts."
Explanation
This Hadīth states the virtue of manumitting Muslim slaves; whoever frees a slave, it is as if he has freed his own entire body from the Hellfire. Freeing Muslim slaves empowers Muslims by ridding them of the humiliation of slavery.
Source · Narrated by Bukhari & Muslim
From the Hadith Encyclopedia (hadeethenc.com).