Doubts about an act whose time of performance has passed

1177. If a person doubts while offering prayers as to whether or not he has performed a particular obligatory act, like, if he doubts whether or not he has recited Surah Al – Hamd, and if he has not engaged himself in the next act (like reading the next Surah), he should perform the act about which he doubted, and if he has engaged himself in the next act, then he should ignore the doubt.