عَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ وَعَنِ الْحَسَنِ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ: ((إِذَا صَامَ أَحَدُكُمْ يَوْمًا فَنَسِيَ فَأَكَلَ وَشَرِبَ فَلْيُتِمَّ صَوْمَهُ فَإِنَّمَا أَطْعَمَهُ اللَّهُ وَسَقَاهُ))
It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) and Sayyiduna Hasan (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him and his family) said: When any one of you is fasting and he eats or drinks forgetfully, then he should complete his fast, for it is Allah Almighty who has fed him and given him drink.