Sahih Muslim
Sahih Muslim 1155
The one who eats, drinks, or has intercourse by mistake does not break his fast
Arabic hadith text
وَحَدَّثَنِي عَمْرُو بْنُ مُحَمَّدٍ النَّاقِدُ، حَدَّثَنَا إِسْمَاعِيلُ بْنُ إِبْرَاهِيمَ، عَنْ هِشَامٍ الْقُرْدُوسِيِّ، عَنْ مُحَمَّدِ بْنِ سِيرِينَ، عَنْ أَبِي هُرَيْرَةَ، - رضى الله عنه - قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم "مَنْ نَسِيَ وَهُوَ صَائِمٌ فَأَكَلَ أَوْ شَرِبَ فَلْيُتِمَّ صَوْمَهُ فَإِنَّمَا أَطْعَمَهُ اللَّهُ وَسَقَاهُ "
Translation
Abu Huraira reported Allah's Messenger (ﷺ) as saying
If anyone forgets that he is fasting and eats or drinks he should complete his fast, for it is only Allah Who has fed him and given him drink.