Musannaf Ibn Abi Shaybah 9725 — Those who said: it is valid only

Abu Wa'il says: We were at a place called Khaniqin. We sighted the moon of Ramadan, and some of us fasted while some of us did not. Then a letter from Sayyiduna Umar (may Allah be pleased with him) came to us, in which it was written: Some new moons are bigger than others. When you see the new moon during the day, do not break the fast until two Muslim men testify that they sighted it the previous evening.