by consensus. This was mentioned by Imam Ahmad and Ibn al-Mundhir, because performing the prayer as four [rak'ahs] became mandatory upon him, so it was not permissible for him to shorten it in number, just as if he had not traveled. Furthermore, he is only performing what he missed, and what he missed was four. As for if he forgets a prayer of travel and remembers it in residency, Ahmad said: 'He must complete it as a precaution.' Al-Awza'i, Dawud, and al-Shafi'i in one of his two views held this same position. Malik, al-Thawri, and the scholars of opinion (Ashab al-Ra'y) said: 'He should pray it as a prayer of travel,' because he is only performing what he missed, and he only missed two rak'ahs. Our argument is that shortening is one of the concessions of travel, so it is nullified by its cessation, like wiping over the socks for three days. Moreover, it became mandatory for him while in residency, based on his statement (peace and blessings of Allah be upon him): 'Let him pray it when he remembers it.' Also, it is an act of worship that differs between residency and travel, so if one of its aspects is found in residency, its ruling prevails, just as if a ship entered the city during the prayer, and like the wiping [over the socks]. Their analogy is invalidated by Friday prayer if it is missed, and by a person who uses tayammum if he misses a prayer and then performs it upon finding water.

Section: If he forgets a prayer in travel and remembers it while in travel, he performs it shortened, because it became mandatory during travel and was performed during it; it is similar to if he had prayed it in its [proper] time. If he remembers it during another travel, it is the same, due to what we have mentioned, regardless of whether he remembers it in residency or not. It is possible that if he remembers it in residency, it becomes binding upon him to perform it in full, because it became mandatory for him to perform it in full by his remembering it, so it remains as a liability upon him. The first view is more appropriate, because its obligation and performance were [intended for] travel, so it is a travel prayer, just as if he had not remembered it in residency. Some of our companions mentioned that a condition for shortening is that the prayer be performed within its time, because it is a shortened prayer, so its time is a condition for it, like Friday prayer. This is invalid, for this is a condition based on opinion and arbitrary assumption that is not supported by the Shari'ah, and the analogy to Friday prayer is not correct.