Bulugh al-Maram, Book 15, Hadith 1420 (In-Book)

Abu Dawud transmitted on the authority of Ka’b bin Murrah (RAA), “The Messenger of Allah said: “Any Muslim woman, who emancipates another Muslim woman, she will be her release from Hell Fire.”

وَلِأَبِي دَاوُدَ: مِنْ حَدِيثِ كَعْبِ بْنِ مُرَّةَ: { "وَأَيُّمَا اِمْرَأَةٍ أَعْتَقَتْ اِمْرَأَةً مُسْلِمَةً, كَانَتْ فِكَاكَهَا مِنْ اَلنَّارِ } 1‏.‏ ‏1 ‏- صحيح.‏ رواه أبو داود ( 3967 )‏، وله شواهد، أحدها الحديث السابق.‏

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also referenced under: Book 15, Hadith 1464 (English)