Muwatta Malik, Book 36, Hadith 1428 (In-Book)

Yahya said that Malik related from Ibn Shihab from Salim ibn Abdullah ibn Umar from his father that Umar ibn al-Khattab said, "What's the matter with men who have intercourse with their slave- girls and then dismiss them? No slave-girl comes to me whose master confesses that he has had intercourse with her but that I connect her child to him, whether or not he has practised coitus interruptus or stopped having intercourse with her."

قَالَ يَحْيَى قَالَ مَالِكٌ عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمِ بْنِ عَبْدِ اللَّهِ بْنِ عُمَرَ، عَنْ أَبِيهِ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، قَالَ مَا بَالُ رِجَالٍ يَطَئُونَ وَلاَئِدَهُمْ ثُمَّ يَعْزِلُوهُنَّ لاَ تَأْتِينِي وَلِيدَةٌ يَعْتَرِفُ سَيِّدُهَا أَنْ قَدْ أَلَمَّ بِهَا إِلاَّ أَلْحَقْتُ بِهِ وَلَدَهَا فَاعْزِلُوا بَعْدُ أَوِ اتْرُكُوا ‏.‏

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also referenced under: Book 36, Hadith 24 (USC-MSA)