Mistake about Four or Five Rak‘at

6. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from Hammad ibn ‘Isa from Shu’ayb from abu Basir who has said the following: “Abu ‘Abd Allah عليه السلام, 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).”’