Sunan Ibn Majah #2522 · The Chapters on Charity

I said to Ka'b bin Murrah, tell us a Hadith from the Messenger of Allah (ﷺ), but be careful. He said: I heard the Messenger of Allah (ﷺ) say: “Whoever frees a Muslim man, he will be his ransom from the Fire; each of his bones will suffice (as a ransom) for each of his bones. Whoever frees two Muslim women, they will be his ransom from the Fire; each of their two bones will suffice (as a ransom) for each of his bones.”