Is the prostration of forgetfulness obligatory for someone who, while rising from the first prostration, remembered that he had performed only one prostration, and so immediately performed the second prostration?

If a worshiper prostrates once and forgets the other, then remembers before standing up, he should return and sit, then perform the second prostration. He is not required to perform thejudgement prostration (sujood al-sahw) for this slight addition, because that whose intentional performance does not invalidate the prayer does not necessitate sujood al-sahw for its forgetful performance.