Yahya related to me from Malik that he had heard that when askedwhether it was permissible for a man to return to his wife if he haddivorced her irrevocably and then another man had married her afterhim and died before consummating the marriage, al-Qasim ibn Muhammadsaid, "It is not halal for the first husband to return to her."Malik said, about the muhallil, that he could not remain in themarriage until he undertook a new marriage. If he had intercourse withher in that marriage, she had her dowry.
USC-MSA web (English) reference: Book 28, Hadith 19
Arabic reference: Book 28, Hadith 1113