He who forgets the prayer, or he slept (and it was omitted), its expiation is (only) that he should observe it when he remembers it.
Sahih Muslim Book 5, Hadith 401
← Previous Hadith This hadith has been narrated by Qatada, but here no mention has been made of" There is no explation for it except this."

Sahih Muslim Book 5, Hadith 400 Next Hadith → When any one of you omits the prayer due to sleep or he forgets it, he should observe it when he remembers it, for Allah has said:" Observe prayer for remembrance of Me."

Sahih Muslim Book 5, Hadith 402