For this report is to be understood as referring to forgetfulness in ‘nawafil’ (recommended prayers), and there is nothing in the report indicating that the doubt occurred in an obligatory prayer (‘fard’). It is also possible that what is meant is a person who frequently forgets and is unable to maintain awareness, in which case it is permitted for him to proceed with his prayer, because if repetition were made obligatory upon him, and forgetfulness is his consistent state, he would never be able to complete a prayer. As for one whose forgetfulness occurs only occasionally, then he is obligated to repeat the prayer, as we have previously stated. What supports what we have mentioned is:
Commentary #13