It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: "Whoever eats or drinks forgetfully while fasting, let him complete his fast, for it is Allah Who has fed him and given him drink."
Sayyiduna Abu Hurairah (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) said: "When any one of you eats or drinks forgetfully while fasting, then remembers, he should complete his fast, for indeed it is Allah who has fed him and given him drink." Imam Darimi (may Allah have mercy on him) said: The people of Hijaz say that in such a case, the fast must be made up, but I say that it does not have to be made up.
Hadith Referenceسنن دارمي / من كتاب الصوم / 1765
Hadith Gradingتحقیق (حسین سلیم أسد الدارانی):إسناده جيد إذا ثبتت الصحية لعم الحارث وهو: عياض بن عبد الله بن سعد بن أبي ذئاب فقد ذكره ابن مندة وأبو نعيم في الصحابة وإلا فهو مجهول والحديث متفق عليه، [مكتبه الشامله نمبر: 1768]