Sayyiduna Ka'b bin Murrah, or Murrah bin Ka'b (may Allah be pleased with him), said: The Prophet (peace and blessings be upon him) supplicated against the tribe of Mudar, so I said: O Messenger of Allah! Allah has granted you that and has answered your supplication, and indeed your people have perished, so pray for rain for them. He (peace and blessings be upon him) said: "O Allah! Grant us rain that brings relief, wholesome, quick in coming, abundant, spreading everywhere, immediate, without delay, beneficial and free of harm." The narrator said: Barely a Friday or so had passed when rain began to fall upon us.
Then it was said to Murrah bin Ka'b: Narrate to us a hadith that you heard from the Messenger of Allah (peace and blessings be upon him) - may Allah have mercy on your father - and be careful. He said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Any servant who frees a Muslim slave, that will be the means of his release from Hell; for every bone of the slave, a bone of the one who freed him will be saved. And any Muslim man who frees two Muslim women, they will both be the means of his release from Hell; for every two bones of theirs, one bone of his will be saved. And any Muslim woman who frees a Muslim woman, she will be the means of her release from Hell; for every bone of hers, a bone of the woman who freed her will be saved."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17886