وَحَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ يَحْيَى بْنِ سَعِيدٍ، أَنَّهُ قَالَ سُئِلَ زَيْدُ بْنُ ثَابِتٍ عَنْ رَجُلٍ، تَزَوَّجَ امْرَأَةً ثُمَّ فَارَقَهَا قَبْلَ أَنْ يُصِيبَهَا هَلْ تَحِلُّ لَهُ أُمُّهَا فَقَالَ زَيْدُ بْنُ ثَابِتٍ لاَ الأُمُّ مُبْهَمَةٌ لَيْسَ فِيهَا شَرْطٌ وَإِنَّمَا الشَّرْطُ فِي الرَّبَائِبِ ‏.‏

Yahya related to me from Malik from Yahya ibn Said that Zayd ibnThabit asked whether it was halal for a man who married a woman andthen separated from her before he had cohabited with her, to marry hermother. Zayd ibn Thabit said, "No. The mother is prohibitedunconditionally. There are conditions, however about foster-mothers." Translation Not Available

Book Ref: Muwatta Imam Malik Book 28 Hadith 1116
Web Ref:  Muwatta Imam Malik Book 28 Hadith 22