📖 Abu Huraira RadhiAllahu 'anhu narrated: Allah's noble Messenger Muhammad SallAllahu 'alaihi wa sallam said, "Whoever eats or drinks forgetfully while he is fasting (whether it is an obligatory or Sunnah voluntary fast), let him complete his fast for Allah (Subhaanahu wa Ta'aala the Most Merciful) has fed him and given him drink."
Source: Sahih Al-Bukhari 1933, Sahih Muslim 1155
Grade: Muttafaqun Alayhi (Authenticity agreed upon) according to Al-Bukhari and Muslim