Do contemporary jurists base the requirement of sighting the crescent moon after sunset on anything, despite the Prophet’s (peace be upon him) hadith not restricting the sighting to sunset and the availability of modern means that allow for its sighting before sunset?

Allah made the moon a sign of the night, and all rulings related to it are established by its sighting at night, not during the day. For this reason, jurists have explicitly stated that the eclipse prayer (Salat al-Khusuf) is not performed if the moon appears eclipsed during the day, due to the cessation of its dominion.

The majority of scholars hold that sighting the crescent moon during the day has no legal implications. Daytime sighting is not considered valid; rather, validity lies solely in sighting the crescent moon after sunset. The hadiths that linked fasting and breaking fast to the sighting of the crescent moon refer to its sighting at night, not during the day.

Many jurists have stated that if the crescent moon is sighted during the day, it pertains to the upcoming night, not the preceding one. This is not a matter of establishing a legal effect based on a daytime sighting of the crescent moon; rather, it is a statement of the actual situation and a refutation of those who claim it belongs to the preceding night.