Muwatta Malik, Book 29, Hadith 8 (USC-MSA)

Yahya related to me from Malik from Yahya ibn Said from al-Qasim ibn Muhammad that a certain man had taken a slave-girl belonging to somebody else as a wife. He said to her people, "She is your concern," and people considered that to be one pronouncement of divorce.

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنِ الْقَاسِمِ بْنِ مُحَمَّدٍ، ‏.‏ أَنَّ رَجُلاً، كَانَتْ تَحْتَهُ وَلِيدَةٌ لِقَوْمٍ فَقَالَ لأَهْلِهَا شَأْنَكُمْ بِهَا ‏.‏ فَرَأَى النَّاسُ أَنَّهَا تَطْلِيقَةٌ وَاحِدَةٌ ‏.‏

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also referenced under: Book 29, Hadith 1160 (In-Book)