It is narrated from Sayyidah 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, upon sighting the crescent of Ramadan, he would fast. And if it was cloudy for him, he (peace and blessings be upon him) would count thirty days of Sha'ban and then fast.