وَحَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا عَبْدُ الأَعْلَى، حَدَّثَنَا سَعِيدٌ، عَنْ قَتَادَةَ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ قَالَ نَبِيُّ اللَّهِ صلى الله عليه وسلم ‏"‏ مَنْ نَسِيَ صَلاَةً أَوْ نَامَ عَنْهَا فَكَفَّارَتُهَا أَنْ يُصَلِّيَهَا إِذَا ذَكَرَهَا ‏"‏ ‏.‏

Qatada narrated on the authority of Anas b. Malik that the Messenger of Allah (PBUH) 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. Translation Not Available

Book Ref: Sahih Muslim Book 5 Hadith 1456
Web Ref:  Sahih Muslim Book 4 Hadith 684 c