Ibn Khuwaiz Mandad said: The minimum duration of menstruation and postpartum recovery, and their maximum, as well as the minimum duration of pregnancy and its maximum, are to be taken on scholarly opinion [ijtihad, independent legal reasoning], since knowledge of this belongs to Allah alone. A ruling is not to be made on any of this except according to what has been made clear to us. Such has been apparently observed in women rarely or customarily, and when we find a woman that has been pregnant for four or five years, we give judgment regarging this; and for postpartum recovery and menstruation, when we find no firm directives, we fall back on what is rare among women.