When the new crescent is seen by day, does it belong to the past night or the coming one?

In the book of fasting in Bidayat al-Mujtahid, Ibn Rushd reports the jurists' disagreement over the time at which the new crescent is seen: they agree that if it is seen in the evening the month begins the next day, and they differ when it is first seen at other times of the day. ¹

• The majority: the moon, at whatever time of day it is first seen, belongs to the coming day, like a sighting in the evening; held by Malik, al-Shafi'i, Abu Hanifa and most of their followers. ¹
• Distinguishing by noon: Abu Yusuf among Abu Hanifa's followers, al-Thawri, and Ibn Habib among Malik's said: if it is seen before noon it belongs to the past night, and if after noon to the coming one. ¹

Ibn Rushd says there is no report from the Prophet ﷺ on the matter to refer to, but two reports are related from Umar ibn al-Khattab, one general and one specific; some followed the general one and some the specific. ¹ The general one is related by al-A'mash from Abu Wa'il Shaqiq ibn Salama: Umar's letter reached us while we were at Khaniqin, saying crescents differ in size, so if you see the crescent by day do not break the fast until two men testify that they saw it the evening before. ¹ The specific one is related by al-Thawri: Umar heard that some people saw the crescent after noon and broke their fast, and wrote reproaching them, saying: if you see the crescent by day before noon, break the fast; if you see it after noon, do not. ²

Ibn Rushd gives the cause of the disagreement as "neglecting experience in a matter whose path is experience, and resorting to reports instead". ¹ He says: what reasoning and experience show is that the moon is not seen while the sun has not set unless it is far from it, since it is then beyond the arc of visibility, and he thinks it unlikely to grow large enough to be seen before sunset; so experience is what counts, there is no difference between before and after noon, and what matters is whether the sun has set. ² The editor of the Bayt al-Afkar edition gives this as an example of Ibn Rushd's use of astronomy. ³

Just before, Ibn Rushd reports that the majority read the hadith "if it is clouded over, estimate it" as completing thirty days, because of the specific hadith of Ibn Abbas; that some early authorities held one should turn to calculation of the courses of moon and sun, the view of Mutarrif ibn al-Shikhkhir; that Ibn Surayj reported from al-Shafi'i that one whose method is inference from the stars and lunar mansions, and who then finds by it that the crescent would be visible though clouded, may begin the fast and it counts; and that Ibn Umar fasted the day of doubt. ¹ Ibn Rushd considers the majority view "clear" here, since the general statement is read in the light of the specific one. ¹

In the Book of Fasting of al-Muhalla, Ibn Hazm says that a crescent seen before noon belongs to the previous night, so people fast from then on for the rest of their day if it is the start of Ramadan and break the fast if it is the end, while one seen after noon belongs to the coming night. ⁴ His proof is the Prophet's saying 'fast when you see it and break the fast when you see it': the case of a sighting after noon is excluded from its apparent sense by certain consensus, so that fasting is due only from the next day, while a sighting before noon remains under the wording of the hadith because it is disputed, and the text must then be followed; he adds that one who sees the crescent before noon sees it with the sun between him and it, which is only possible if it rose the previous evening and has moved far from the sun. ⁴

He relates from Ibrahim al-Nakha'i that 'Umar ibn al-Khattab wrote to the people, 'If you see it before the sun passes the meridian, break the fast; if you see it after, do not', and that Sufyan al-Thawri held this; from 'Ali a similar ruling, explained by the sun's moving away from it; and from al-Rabi' that he saw the crescent in the forenoon with Salman ibn Rabi'a al-Bahili at Balanjar, and Salman ordered the people to break the fast. ^{4 5} He names 'Abd al-Malik ibn Habib al-Andalusi and Abu Bakr ibn Dawud as holding the same view, and answers the objection that the opposite is also reported from 'Umar by saying that, where a dispute is established, the matter goes back to the Qur'an and the Sunna. ⁵

Modern astronomy and contemporary astronomical calculation of visibility are not given here; the page is limited to what Ibn Rushd reports.