Simak bin Harb said: I woke up one morning when it was difficult for me to know whether it was Sha'ban or a day of the month of Ramadan, so I fasted. I went to Ikrimah and saw that he was eating bread and vegetables. He said: Come and eat food. I said: I am fasting. Ikrimah said: I swear by Allah, you must break your fast. When I saw that he had sworn an oath and did not say "insha'Allah," I went ahead and ate heartily, even though a little while before I had taken suhoor. After that, I said: Now tell me, what do you have regarding this matter? He said: Ibn Abbas (may Allah be pleased with them both) narrated to us that the Messenger of Allah (peace and blessings be upon him) said: "Fast when you see the crescent and break your fast when you see the crescent. If clouds come between you and the crescent, then complete thirty days (of Sha'ban), and do not fast in anticipation of Ramadan."