It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: Begin fasting by sighting the moon and stop fasting by sighting the moon. If clouds come between you and the moon, then complete the count (thirty) of the previous month, and do not fast just before (the arrival of) the month of Ramadan. Hatim, the narrator, says: The Prophet (peace and blessings be upon him) meant that the count of Sha'ban should be completed.

. (Second chain) It is stated in this: If a cloud comes between you and the moon, then complete the counting, and the month can also be of (29) days. That is, it can also be one day less than thirty (30).

It is narrated from Sayyida Aisha (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) used to pay more attention to the crescent of Sha'ban than to the crescent of any other month. Then, when the crescent of Ramadan was sighted, he would begin fasting, and if the sky was cloudy, he would complete the count of thirty days of (Sha'ban), and then begin fasting.