Abu Dawud Book 7, Hadith Number 2318.
Chapter : Not known.
Narated By ‘Aisha, Ummul Mu’minin : The Apostle of Allah (PBUH) used to count the days in Sha’ban in a manner he did not count any other month; then he fasted when he sighted the new moon of Ramadan; but if the weather was cloudy he counted thirty days and then fasted.