(a) It is narrated from Sayyiduna Anas (may Allah be pleased with him) that Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him) led the people in the morning prayer and recited Surah al-Baqarah. Sayyiduna Umar (may Allah be pleased with him) said to him that the sun was about to rise, and he said: If it had risen, it would not have found us heedless.
(b) A narration with the same meaning is reported through Qatadah (may Allah have mercy on him) from Sayyiduna Anas (may Allah be pleased with him). In it is: "kadat al-shams" (the sun was about to rise).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4015