مسائل المنتخبه (Articles Of Islamic Acts) - الخوئي، السيد أبوالقاسم - الصفحة ٢٥٦ - DOUBTS IN CONNECTION WITH PRAYERS

(i) Doubt about the act the time whereof has already passed (e.g. during bowing a person doubts as to whether he did or did not recite Surah al-Hamd).
(ii) Doubt after the salaam (salutation) of prayers.
(iii) Doubt after the time for prayers has already passed.
(iv) Doubt of a person who doubts too much.
(v) Doubt by the Imam (one who leads the congregation prayers) about the number of units when the mamum (follower) is aware of their number and similarlythe doubt of the mamum when the Imam knows the number of units.
(vi) Doubt which occurs in recommended and precautionary prayers.

I. Doubt About an Act Whose Time has Passed
١١٧٧. If a person doubts, while offering prayer, as to whether or not he has performed an obligatory act of the prayers (e.g. he doubts whether or not he hasrecited Surah al-Hamd) and has not yet engaged himself in the next act, he should perform the act, about which he has a doubt. In case. however, he has already engagedhimself in the act which he had to perform later (e.g. if he doubts while reciting the other surah as to whether or not he has recited Surah al-Hamd) he should ignore hisdoubt.
١١٧٨. If a person doubts. while reciting a verse, whether or not he has recited the preceding verse, or doubts while reciting the later part of a verse whether ornot he has recited its earlier part, he should ignore his doubt.
١١٧٩. If a person doubts after bowing or prostration whether or not he has performed its obligatory acts, like recitation and calmness of body. he should ignore hisdoubt.
١١٨٠. If, while going into prostration, a person doubts whether or not he has performed bowing, he must return and stand up and perform bowing, and if he doubtswhether or not he stood