(11) CHAPTER. The statement of the Prophet, peace be upon him, “Start observing Saum (fasts) on seeing the crescent-moon of Ramadan, and stop observing Saum on seeing the crescent-moon (of Shawwãl).’ And ‘Ammãr said, “Whoever observes Saum (fasting) on a doubtful day* is disobeying Abül-Qasim (i.e., the Prophet, peace be upon him)
1906. Narrated ‘Abdullah bin ‘Umar: Allah’s Messenger, peace be upon him, mentioned Ramadan and said, “Do not observe fasting unless you see the crescent-moon (of Ramadan), and do not give up fasting till you see the crescent-moon of (Sawwäl), but if the sky is overcast and you can’t see the moon, then act on estimation (i.e., count Sha’bãn as 30 days and Ramadan also as 30 days).”
*The doubtful day is the day that is not certainly the first of Ramadan, but perhaps the last of Sha’ban, the preceding month.