Narrated Abu Huraira: Allah's Apostle said, "When the month of Ramadan starts, the gates of the heaven are opened and the gates of Hell are closed and the devils are chained."
Hadith Referenceصحيح البخاري / كتاب الصوم / 1899
Hadith Gradingمحدثین:أحاديث صحيح البخاريّ كلّها صحيحة
Narrated Ibn `Umar: I heard Allah's Apostle saying, "When you see the crescent (of the month of Ramadan), start fasting, and when you see the crescent (of the month of Shawwal), stop fasting; and if the sky is overcast (and you can't see it) then regard the month of Ramadan as of 30 days."
Hadith Referenceصحيح البخاري / كتاب الصوم / 1900
Hadith Gradingمحدثین:أحاديث صحيح البخاريّ كلّها صحيحة