´It was narrated that Anas said:` "The Messenger of Allah (ﷺ) was asked about a man who slept and missed the prayer, or forgot it. He said: 'The expiation for that is to pray it when he remembers it.'"
Hadith ReferenceSunan an-Nasa'i / The Book of the Times (of Prayer) / Hadith: 615
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:صحيح
Hadith Takhrij«سنن ابن ماجہ/الصلاة 10 (695)، مسند احمد 3/267، (تحفة الأشراف: 1151) (صحیح)»