Mistake about Four or Five Rak‘at

“I once heard abu Ja‘far (a.s.), say, ‘The Messenger of Allah has said, “If one of you doubts in his Salah (prayer) and does not know if he has increased or decreased, he performs two Sajdah (prostration) while sitting.” The Messenger of Allah has called it humiliating (Satan).’”

“Abu Ja‘far (a.s.), has said, ‘If one of you is certain that he has increased something in his obligatory Salah (prayer) he does not depend on it and performs his Salah (prayer) again if he is certain of such increase.’”

“Abu ‘Abd Allah (a.s.), has said, ‘If you do not know whether you have performed four or five; then perform two Sujud (prostrations) because of mistake after Salam (the phrase of offering greeting of peace) and after the two Sujud (prostrations), say Salam.’”

“He (the Imam) (a.s.), has said, ‘If one knows the kind of mistake he has made and completes it then Sajdah (prostration) for mistake is not necessary for him. Sajdah (prostration) for mistake is upon one who does not know if he has increased or decreased something in Salah (prayer).”’

“Abu ‘Abd Allah (a.s.), has said, ‘If one increases something in his Salah (prayer) he performs it again.’”

“Abu ‘Abd Allah (a.s.), has said, ‘If you do not know whether you have performed five Rak‘at or four, perform two Sajdah (prostration) because of mistake after Salam (the phrase of offering greeting of peace) in a sitting position and thereafter say Salam (the phrase of offering greeting of peace).”’