One sajda forgotten: will sajda al-sahw make the prayer valid?

Question

In prayer [a person] forgot one sajda and then performed sajda al-sahw at the end. Did the prayer become valid or not? One [sajda] is fard and the other wajib; bear in mind that the sajda he forgot is the second one. Are both sajdas fard, or is one fard and the other wajib? Some people say that the word “sajdatan” (two sajdas) does not occur in the books of fiqh, so how can both be fard?

Answer

Both sajdas are fard. Leaving out a fard makes the prayer fasid, and repeating it (i‘ada) is necessary; sajda al-sahw is not sufficient. The second sajda is explicitly mentioned in the books of fiqh. (It is in “Kabiri”, p. 313, “al-Bahr al-Ra’iq”, vol. 1, p. 293, “Radd al-Muhtar”, vol. 1, p. 300 and in all the other books.)

Source: Fatawa Mahmudiyya

Preview. The full text opens with JavaScript enabled.