Ali bin Hanzalah (may Allah be pleased with him) narrates from his father: We were with Umar (may Allah be pleased with him) when a large bowl was brought in the month of Ramadan. The muezzin said: "The sun is still up." He said: "May Allah protect us from your evil! We did not send you to watch the sun; we sent you to call to the prayer." Then he said: "O people, whoever of you has broken his fast, making up a day is easy; otherwise, let him complete his fast."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8013