So this does not contradict the first report, because one who sat in the fourth rak‘ah and then stood and prayed an additional rak‘ah has not invalidated any of the essential pillars (‘arkan’) of the prayer. Rather, what he omitted was the ‘taslim’, and omitting the ‘taslim’ does not necessitate repeating the prayer, as we have previously explained. And whenever one doubts whether he is in the fourth or the fifth rak‘ah, he should build upon the fourth, give the ‘taslim’, and then perform the two prostrations of forgetfulness (‘sajdatay al-sahw’), which are known as ‘al-marghimatan’ (the two that humiliate (Shaytan)).
Commentary #24