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."
USC-MSA web (English) reference: Book 28, Hadith 22
Arabic reference: Book 28, Hadith 1116