Nafi’ (may Allah have mercy on him) narrated: I was with Abdullah (may Allah be pleased with them both) while he was in the state of Ihram. He took a sheet, so I put a cap on him. He asked: What is this? I said: It is a cap. He said: Do you not know that the Messenger of Allah (peace and blessings be upon him) forbade (a person in Ihram) from wearing a cap?