Abu Wa'il narrates: A letter from Sayyiduna Umar (may Allah be pleased with him) came to us while we were in Khanqin (it stated): "The crescent of the first (of the month) sometimes appears small or large, so if you see the moon during the day, then break your fast at sunset, unless two Muslims testify that they saw the moon the previous night (then you may break your fast and celebrate Eid al-Fitr)."