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 No. 614
Sunan an Nasai
Gradings:
Abu Ghuddah:
Sahih
Al-Albani:
Sahih
Zubair Ali Zai:
Sahih