Riyad as-Salihin 1242
Abu Hurairah (May Allah be pleased with him) reported:
The Prophet (ﷺ) said, "If any one of you forgetfully eats or drinks (while observing fasting) he should complete his Saum (fasting), for Allah has fed him and given him to drink." [Al-Bukhari and Muslim] .
وعن أبي هريرة رضي الله عنه عن النبي صلى الله عليه وسلم قال‏:‏ ‏
"‏إذا نسي أحدكم فأكل أو شرب فليتم صومه فإنما أطعمه الله وسقاه‏"‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏