Imam Malik's Muwatta, Chapter: Divorce

Yahya related to me from Malik that Yahya ibn Said said that he had heard al-Qasim ibn Muhammad say that Zayd ibn Abd al-Malik separated some men and their wives who were slave-girls who had borne children to men who had died, because they had married them after one or two menstrual periods. He separated them until they had done an idda of four months and ten days. Al-Qasim ibn Muhammad said, "Glory be to Allah! Allah says in His Book, 'Those of you who die, leaving wives, they are not wives.' "