Sunan Ibn Majah, Book 2, Hadith 30 (In-Book) ⓘ
It was narrated that Anas bin Malik said: "The Messenger of Allah said: 'Whoever forgets a prayer, let him perform it when he remembers it.'"
حَدَّثَنَا جُبَارَةُ بْنُ الْمُغَلِّسِ، حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ قَتَادَةَ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ " مَنْ نَسِيَ صَلاَةً فَلْيُصَلِّهَا إِذَا ذَكَرَهَا " .
also referenced under: Hadith 696 (Reference) & Volume 1, Book 2, Hadith 696 (DarusSalam)