Yahya related to me from Malik from Yahya ibn Said and from Yazidibn Abdullah ibn Qusayt al-Laythi that Said ibn al-Musayyab said,''Umar ibn al-Khattab said, 'If a woman is divorced and has one or twoperiods and then stops menstruating, she must wait nine months. If itis clear that she is pregnant, that is that. If not, she must do anidda of three months after the nine, and then she is free to marry.' "
USC-MSA web (English) reference: Book 29, Hadith 70
Arabic reference: Book 29, Hadith 1230