The Prophet ﷺ said, "Whoever forgets a prayer should pray it as soon as he remembers it. There is no expiation for it but that."
حدثنا محمد بن كثير أخبرنا همام عن قتادة
أن النبي ﷺ قال من نسي صلاة فليصلها إذا ذكرها لا كفارة لها إلا ذلك
Sourced from Bukhari, Prayer Times, chapter "Whoever forgets a prayer should pray it when he remembers," etc., no. 597, and Muslim, Mosques, chapter "Making up a missed prayer and the recommendation of hastening to make it up," no. 684, from the hadith of Hammam bin Yahya, with the same chain.