Does the prayer of one who is assailed by doubt during prayer become void if he bases his action on the minimum? And does basing it on the maximum include all actions of the prayer, such as doubting the place of error while reciting Al-Fatiha, and should he repeat the word that is closer in time or the one that is further away?

He who is overwhelmed by doubt in prayer—meaning it occurs frequently, such that he doubts every day, even if only once—should ignore it. There is no need for him to rectify it; rather, he should build upon what is most probable. And if he does rectify it, meaning he builds upon what is less probable, his prayer is not invalidated.

As for Al-Fatihah, it is a pillar of prayer. Whoever makes an error in it that alters the meaning must rectify it. If he is uncertain about the word he erred in—whether it is from the beginning of Al-Fatihah or its end—he should restart it anew.