Abu Wa'il narrates: A letter from Sayyiduna Umar (may Allah be pleased with him) came to us (at the place of Khanqin), in which it was written: "The crescent of the first (of the month) sometimes appears small or large, so when you see the moon in the early part of the day, do not celebrate Eid until two men testify that they saw this moon the previous night."