Sahih Muslim Book - 13, Hadith - 2716

وَحَدَّثَنِى عَمْرُو بْنُ مُحَمَّدٍ النَّاقِدُ حَدَّثَنَا إِسْمَاعِيلُ بْنُ إِبْرَاهِيمَ عَنْ هِشَامٍ الْقُرْدُوسِىِّ عَنْ مُحَمَّدِ بْنِ سِيرِينَ عَنْ أَبِى هُرَيْرَةَ - رضى الله عنه - قَالَ قَالَ رَسُولُ اللَّهِ -صلى الله عليه وسلم- « مَنْ نَسِىَ وَهُوَ صَائِمٌ فَأَكَلَ أَوْ شَرِبَ فَلْيُتِمَّ صَوْمَهُ فَإِنَّمَا أَطْعَمَهُ اللَّهُ وَسَقَاهُ ».

It was narrated that Abu Hurairah [may Allah be pleased with them] said: “The Messenger of Allah said: ’Whoever forgets that he is fasting and eats or drinks, let him complete his fast, for Allah has fed him and given him to drink.’”