Malik (may Allah have mercy on him) narrated to us; he said: I found the people rejecting what some people said from Umar (may Allah be pleased with him), that he said: "Her husband is to be given a choice when he comes": if she has already married, he is to be given the choice between the dowry and the woman. Malik (may Allah have mercy on him) said: When she marries after her 'iddah has ended, then whether he has consummated the marriage with her or not, her first husband has no way to her; and this is the position with us as well. Imam Malik (may Allah have mercy on him) said: If her husband comes before her 'iddah ends, then he has more right to her.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العدد / 15572