at the time of the crescent’s first appearance. This claim is false. The eminent scholars of Islamic law have agreed that relying on this for determining the crescent is forbidden. Sensible practitioners of calculation likewise agree that the crescent’s visibility can never be determined with complete precision by calculation. For this reason, the masters of calculation did not undertake this; rather, they rejected it. Only some of their later practitioners discussed it in approximate terms. This is a departure from Allah’s religion and an alteration of it, resembling the Jews’ and Christians’ departure from what they were commanded concerning the crescent to the sun’s endpoint at the conjunction of the two discs—the period of the moon’s invisibility—rather than crescent-based months, and similar practices.

The postponement practised among the Arabs—which is an increase in disbelief, through which those who disbelieve go astray, permitting it one year and forbidding it another—is what the scholars of hadith, historical biography, Quranic commentary and other disciplines have described.

It is established in the two Sahīh collections, on the authority of Umar, that the Prophet, may Allah bless him and grant him peace, said:

“We are an unlettered nation: we neither write nor calculate. Begin fasting when you sight it, and end fasting when you sight it.”

Whoever determines the crescent—which Allah has made a means of marking time for people and for Hajj—through writing and calculation is unsound in both reason and religion. Even when someone’s calculations are correct, the most he can do is determine the distance between the sun and the moon at sunset, for example. This is what is called the moon’s distance from the sun. But this does not establish that it will certainly be visible, or that it cannot possibly be seen.