its prescribed time has entirely elapsed—this accords with their ruling that someone who has forgotten two prayers from different days, without knowing which preceded the other, such as the noon and afternoon prayers, must perform three prayers: a noon prayer between two afternoon prayers, or an afternoon prayer between two noon prayers. This ensures that he has avoided reversing their order and has performed the forgotten prayers in sequence.
On this view, if he remembers three prayers—the dawn, noon and afternoon prayers—without knowing which preceded the others, he must perform seven prayers, beginning and ending with the dawn prayer. If he remembers four prayers—the dawn, noon, afternoon and sunset prayers—without knowing which preceded the others, he must perform thirteen prayers, likewise beginning and ending with the dawn prayer. If he remembers five prayers—the dawn, noon, afternoon, sunset and night prayers—without knowing which preceded the others, he must perform twenty-one prayers, again beginning and ending with the dawn prayer, since certainty and the required sequence cannot be achieved with fewer prayers.
The general rule for calculating this is always to subtract one from the number of forgotten prayers, then multiply the remainder by their original number, and add to the product the one subtracted [from their number]. Alternatively, subtract one from their number, multiply the remainder by itself, and add the number of prayers to the product. The result is the same.
Section
If someone has forgotten the noon and afternoon prayers, one from Saturday and the other from Sunday, without knowing which belongs to Saturday and which to Sunday, three views may be derived concerning this case. The first is that neither assigning the prayers to particular days nor observing their sequence is taken into account, so he performs only a noon prayer and an afternoon prayer.
The second is that both are taken into account by assigning the prayers to their particular days, since observing their sequence is included in this: there is no doubt that Saturday precedes Sunday. He therefore performs a noon prayer and an afternoon prayer for Saturday, followed by a noon prayer and an afternoon prayer for Sunday, as Ibn Habīb stated. Alternatively, he performs a noon prayer for Saturday, then an afternoon prayer for Sunday, then an afternoon prayer for Saturday, followed by a noon prayer for Sunday, as ‘Īsā transmitted from Ibn al-Qāsim. Both arrangements are valid, because each covers the possibilities about which he is uncertain and thereby ensures that the required sequence is observed