a traveller or a resident. This only occurs in places where travellers are numerous, such as an airport, for example, where there are residents as well as travellers. Sometimes they are identifiable by some sign, and sometimes they are not. If they have some identifying sign, the matter is clear; but if there is no sign, he must complete the prayer because he is uncertain whether shortening it is permissible. The apparent meaning of the author’s words is that he must complete it even if it later becomes clear that the imam was a traveller.

The stronger view, in my opinion, is that in this case he is not required to complete the prayer, because the basic ruling for a traveller’s prayer is shortening it. He is only required to complete it behind the imam if the imam completes it, whereas here the imam did not complete it.

If, upon seeing an imam leading the people in a place shared by travellers and residents, he says, “If my imam completes the prayer, I will complete it; and if he shortens it, I will shorten it,” this is valid, even though it is conditional. For this condition conforms to the actual state of affairs: if his imam shortens the prayer, then shortening is obligatory for him; and if he completes it, then completing it is obligatory for him. This is not a matter of doubt; rather, it is a case of making an action conditional upon its causes. The cause for completing the prayer here is the imam’s completing it, while shortening is the basic ruling.

His statement: “Or he begins a prayer which he is required to complete, then it becomes invalid and he repeats it.”

This is the seventh issue: that is, a traveller begins a prayer which he is required to complete, such as when he prays behind a resident. He has thus begun a prayer which he is required to complete. If it becomes invalid due to ritual impurity or otherwise, and he then repeats it, he is required to complete it, because this prayer is a repetition of a prayer that must be completed. Therefore, he must pray four units.

Note: If a traveller joins a resident imam and, after beginning the prayer, remembers that he is not in a state of ablution, so he leaves and performs ablution, but when he returns finds that the people have finished praying, then he is not required to complete the prayer. This is because the author says: “Or he begins