The source of their disagreement lies in the ambiguity found in the Prophet’s ﷺ words:
“Fast when you sight it and break the fast when you sight it; but if it is obscured from you, fa-qdurū lahu.”

The majority understood the phrase fa-qdurū lahu to mean: “complete the number to thirty (days).” Others held that “estimate for it” means to calculate it by astronomical reckoning, while a third group maintained that its meaning is to begin the day fasting—­the opinion of Ibn ʿUmar, as noted earlier, though the wording hardly supports it.

The majority adopted their reading because of the sound ḥadīth reported from Ibn ʿAbbās in which the Prophet ﷺ said:
“If it is obscured from you, then complete the number to thirty.”

The former text is ambiguous, whereas this one is explicit; hence the ambiguous must be interpreted in light of the explicit. This is an undisputed principle among the legal theorists, for in their view an ambiguous text and its clarifying counterpart never truly conflict. The position of the majority is therefore evident—­and Allah knows best.

As for their divergence regarding the time of sighting: they agree that if the crescent is seen at dusk, the month is deemed to begin on the following day. They differ, however, when the first sighting occurs at any other time during daylight—­that is, the very first moment it is observed.

The majority hold that a crescent first seen in the daytime counts for the coming day, exactly as if it had been seen at dusk. This is the view of Mālik, al-Shāfiʿī, Abū Ḥanīfah, and the bulk of their disciples.

Abū Yūsuf (of Abū Ḥanīfah’s school), al-Thawrī, and Ibn Ḥabīb (of Mālik’s school) said: if the crescent is sighted before noon it belongs to the preceding night; if it is sighted after noon it belongs to the night to come.

The cause of their disagreement is their failure to rely on empirical observation in a matter whose proper avenue is experiment, and their recourse instead to transmitted reports—­while no Prophetic report exists on the point. Only two reports from ʿUmar—may Allah be pleased with him—have come down to us, one general and the other explicit; some scholars followed the general wording, others the explicit.

1. The general report: al-Aʿmash narrated from Abū Wāʾil Shaqīq ibn Salamah who said, “A letter from ʿUmar reached us while we were in Khāniqīn stating: ‘The crescents differ in size. If you see the crescent during the day, do not break the fast until two men testify that they saw it the previous evening.’”

2. The explicit report: al-Thawrī related that news reached ʿUmar ibn al-Khaṭṭāb that some people saw the crescent after noon and broke their fast. He wrote rebuking them and said, “If you see the crescent during the day before noon, break the fast; but if you see it after noon, do not break the fast.”

The Qāḍī comments: Analogy and experience both indicate that the moon cannot be seen while the sun has not yet set except