"Whoever eats out of forgetfulness while fasting, let him complete his fast, for it is Allah Who has fed him and given him to drink."
Sunan Ibn Majah Book 7, Hadith 36
← Previous Hadith “Whoever does not fast one day in Ramadan without having a concession allowing that, fasting for a lifetime will not make up for that.”

Sunan Ibn Majah Book 7, Hadith 35 Next Hadith → “We broke our fast on a cloudy day at the time of the Messenger of Allah (ﷺ), then the sun appeared.” I (one of the narrators) said to Hisham: "Were they commanded to make up for that day?" He said: "It had to be made up." (According to Hisham's opinion).

Sunan Ibn Majah Book 7, Hadith 37