If anyone emancipates a Muslim slave, Allah will set free from Hell an organ of his body for every organ of his (slave's) body. (Using translation from Muslim 1509a)
قَالَ رَسُولُ اللهِ ﷺ «مَنْ أَعْتَقَ رَقَبَةً مُؤْمِنَةً أَعْتَقَ اللهُ بِكُلِّ إِرْبٍ مِنْهَا إِرْبًا مِنْهُ مِنَ النَّارِ» حَتَّى إِنَّ اللهَ لَيَعْتِقُ بِالْيَدِ الْيَدَ وَبِالْفَرْجِ الْفَرْجَ