Question
When is it necessary to do Sujood as-Sahw (the prostration of forgetfulness)?
Answer
Allah made it obligatory to perform the Sujood As-Sahw, and he did not permit leaving it. The Prophet said: ‘When any one of you gets up and prays, Satan comes to him and confuses him until he does not know how many Rak’ahs (units) he prayed. If any one of you notices that, let him prostrate twice when he is sitting.’ [Nasai 1252; Sahih]
Allah mentioned three scenarios where it becomes obligatory to perform the prostration of forgetfulness:
1. Forgetfulness
Allah commanded the Muslim to perform Sujood As-Sahw when he forgets performing something related to the acts associated with his prayer. The Messenger of Allah said: ‘If one of you falls prey to forgetfulness in his prayer, he should offer two prostrations of forgetfulness.’ [Muslim 572l]
2. Doubt
Allah commanded the Muslim to perform Sujood As-Sahw when he is confused/is doubtful of whether he performed something related to the acts associated with his prayer. The Messenger of Allah said: ‘Whoever has doubt or is not sure [regarding how many Rak’ahs he’s prayed or whether he performed an act related to the prayer or not], let him estimate what is correct, then let him offer two prostrations of forgetfulness.’ [Nasai 1246; Sahih]
3. ADDition and omission
Allah commanded the Muslim to perform Sujood As-Sahw when he adds or omits something related to the acts associated with his prayer. The Messenger of Allah said: ‘If a person adds or omits something in his prayer, he should perform two prostrations of forgetfulness.’ [Muslim 572n]