Narrated Ibn Umar (RA): I heard Allah's Messenger (SAW) saying, "When you see the crescent (of the month of Ramadan), start observing Saum (fast), and when you see the crescent (of the month of Shawwal), stop observing Saum (fast); and if the sky overcast (and you can't see it) then regard the crescent (month) of Ramadan (as of 30 days)."
