Muwatta Imam Malik Book of Marriage, Hadith 22

Yahya related to me from Malik from Yahya ibn Said that Zayd ibn Thabit asked whether it was halal for a man who married a woman and then separated from her before he had cohabited with her, to marry her mother. Zayd ibn Thabit said, "No. The mother is prohibited unconditionally. There are conditions, however about foster-mothers."

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 .