It is narrated from Mak'hool (may Allah have mercy on him) that it was asked from Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him): If a person has taken suhoor and thinks that it is still night, while in fact Fajr has already risen, then Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) said: If this is in the month of Ramadan, then he should fast and make up for that day, and if it is a fast of any month other than Ramadan, then he may eat for the rest of the day because he began the day (in that state).
Hadith Referenceسنن سعید بن منصور / كتاب التفسير / 281
Hadith Gradingمحدثین:سنده ضعيف للانقطاع بين مكحول وأبي سعيد الخدري
Hadith Takhrij«أخرجه سعيد بن منصور فى (سننه) برقم: 281، والبيهقي فى(سننه الكبير) برقم: 8107»