What is the evidence for Sheikh al-Islam Ibn Taymiyyah's statement that the crescent is the sighting by people, and not what appears in the sky, and how is this explained in light of the saying of the Messenger of Allah, peace and blessings be upon him: "If you see it"? And does this invalidate the fast of one who sights the crescent alone?

Sheikh Al-Islam Ibn Taymiyyah held that the crescent (hilal) is the name for what becomes apparent (istahalla) to people, and the month (shahr) is what becomes well-known (ishtahara) among them, basing his argument on the following: 1. Allah linked religious rulings, such as fasting and breaking the fast, to the crescents and the month. The word hilal is derived from istihlal (to become apparent or to appear), and shahr from ishtihar (to become well-known). Therefore, what has not appeared or become well-known among people is not a hilal or a shahr. 2. Analogy with the crescent of Dhul-Hijjah: no one acts upon a solitary sighting of it. Why should the matter be different in Ramadan? 3. The hadith: "Fasting is the day you fast, and breaking the fast is the day you break fast, and Eid al-Adha is the day you offer sacrifice." This indicates that these rituals are to be observed with the Muslim community.

This is a matter of ijtihad (independent juristic reasoning), and a Muslim is required to act upon what he finds most compelling from the religious evidence. If one is not comfortable with the above and believes that one who sights the crescent alone is obligated to fast, then he should act accordingly.

Sheikh Ibn Uthaymeen, however, held that whoever sights the crescent and is certain of his sighting in a remote place where no one else is with him, is obligated to fast, based on the generality of Allah's statement: "So whoever sights [the new moon of] the month, let him fast it" (Quran 2:185) and the Prophet’s saying: "When you see it, then fast." If he is in a town and testifies before the court, but his testimony is rejected, he should fast secretly.