The Prophet ﷺ said, "Whoever forgets a prayer should pray it as soon as he remembers it. There is no expiation for it except that. 'And establish prayer for My remembrance' [Taha 20:14]."
عن النبي ﷺ قال: من نسى صلاة فليصل إذا ذكرها، لا كفارة لها إلا ذلك، {وأقم الصلوة لذكرى} [سورة طه: ١٤].
Bukhari narrated it in "The Prayer Times" (597) from Abu Naeem and Musa bin Ismail, who both said, "Hammam narrated to us, from Qatada, from Anas," and he mentioned something similar.Musa said, Hammam said, "I heard him say afterward, "And establish prayer for My remembrance"[Taha 20:14]."Habban said, "Hammam narrated to us, Qatada narrated to us, Anas narrated to us, from the Prophet ﷺ," similarly.Muslim narrated it in "The Mosques" (684) from Haddab bin Khalid, "Hammam narrated to us," with the same wording.He also narrated it through other routes from Abu Awana, from Qatada, with the same wording, but without mentioning "There is no atonement for it except that."Bukhari titled his chapter, "Whoever forgets a prayer should pray it when he remembers it, and he need not repeat any prayer except that one." From this it is understood that nothing is required beyond repeating that prayer.Malik held the view that whoever remembers, after having prayed a prayer, that he had not prayed the one before it, should pray the one he remembered, then pray the one he had already prayed, in observance of the proper order. End of quote.It is possible that by his statement, "he need not repeat any prayer except that one," he was alluding to what occurs in some routes of the hadith of Abu Qatada in Muslim, in the account of oversleeping past a prayer, where he said, "If it is the next day, let him pray it at its time." Thus the repetition happens twice, once when he remembers it, and once when its like comes around at the coming time.See Fath al-Bari (2/71), and this is the hadith of Abu Qatada that follows.