(55) باب قَضَاءِ الصَّلاَةِ الْفَائِتَةِ وَاسْتِحْبَابِ تَعْجِيلِ قَضَائِهَا
Qatada narrated on the authority of Anas b. Malik that the Messenger of Allah (ﷺ) said:
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.
Reference: Sahih Muslim 684 c
In-book reference: Book 5, Hadith 404
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1456