Qatadah (may Allah have mercy on him) narrates from Sa'id bin al-Musayyib (may Allah have mercy on him) concerning a man who had four wives and divorced one of them. He said: "If he wishes, he may marry a fifth during her waiting period." He said the same concerning two sisters.
(b) Qatadah (may Allah have mercy on him) narrates from Sa'id bin al-Musayyib (may Allah have mercy on him) concerning a woman who has been irrevocably divorced.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13851