Currently, the issue of moonsighting is creating much confusion in many countries, Can we have an overview of opinions on moonsighting from classical scholars mainly Imam Abu Hanifa, Imam Malik, Imam Shafi'i and Imam Ahmad Ibn Hanbal with references from authoritative books from these scholars?
According to the nice book of sheikh al-Bouti called lectures in comparative jurisprudence محاضرات في الفقه المقارن were the first chapter or example is about the issue whether moonsighting at a location is binding for other or not he quoted two opinions:
A sighting at a location is not binding for an other location which is far away from it. This is (according his book) the view of the Shafi'i school (in the practiced or applied madhab), az-Zayla'i amoung the Hanafi school, and Malik according his Medinean students like ibn al-Majashoon and al-Mughira and it is also the view of the scholars 'Ikrimah, al-Qasim and Ishaaq ibn Rahawayh.
This fatwa in Arabic says it is the madhab of a-Shafi'i himself, while the other view is the one of Abu Hanifa and Ahmad.
- A sighting in any location is binding for this location and any other, so if some people began fasting Saturday and later realized or heard that others started on Friday they will have to make up one day!
This is the view of the Hanafi and Hanbali school and the view of Malik according his Egyptian studtens like ibn al-Qassim and also narrated to be the view of al-Muzni the student of a-Shafi'i.
And he added some remarks:
- Some scholars pretended that there's a consensus that if the distance between both locations is very big like between al-Hijaz (Mekka-Medina) and al-Andalus (Spain) then each location should fast for itself, al-Qurtobi, ibn 'Abd al-Barr, ibn Hajar and ibn Rushd (the grandson) pretended that there's consensus about this. But an-Nawawi in his Majmoo' quoted that some scholars insisted that once a sighting anywhere has been made all people on earth must fast!
- The dispute ends once the great Imam (a Caliph or so) the Emir of believers declared the beginning of Ramadan himself, in this case every Muslim is asked to follow this order no matter how close or far he is living from that location.
Now to the evidences for each View:
First view: For example in sahih Muslim based on the statement of ibn 'Abbas: "He said: No; this is how the Messenger of Allah (ﷺ) has commanded us."
And again in sahih Muslim (and three ways in al-Muwatta'), according this seeing the crescent is necessary to start or end fasting!
Also it was not reported that any of the caliphs sent out any messenger to inform people or order them to start fasting, so people totally relayed on the local sighting!
Then based on Qiyas different location lead to different times and prayer times therefore to different moon-sightings.
And finally a logical basis is that Allah ordered fasting for a specific time, which is related to the movement of planets, times differ with the "distance" of (different) locations therefore the fasting time should differ.
Second view: For example this hadith from sahih Muslim, based on the fact that it addresses all the Muslims -as our Prophet used the plural- and the order to fast according a sighting seems to be general (not specific to a location), no matter if it is based on a single witness or more as long as the person is trustworthy.
The Qiyas of far or distant locations to the surroundings as there's no clear evidence for a difference in the ruling.
Al-Bouti also discussed the evidences and tried to show up what is the more correct he also quoted the reason for the differences based on osol al-Fiqh
For example Hanafi school rejected the ahad that's why they rejected the hadith of ibn 'Abas, as the man who informed him was a single person so his witness is neglected.
Then the dispute about the meaning of a general "statement" whether it applies or not so Shafi'i and the majority of the scholars of osol for example rejected the meaning taken in the second view as they considered this statement to be only a kind of a conjectural evidence not a positive proof. Which means it is general but doesn't mean all Muslims, rather than all present Muslims.
How many witnesses are needed for the sighting to apply for the beginning and end of Ramadan?
The majority of scholars say for the beginning of Ramadan only one witness is need (based on the hadith of the bedouin compiled by an-Nasa'i and abu Dawod, and the hadith of ibn 'Omar) while for the end two are needed (this is quoted by at-Tirmdihi in his comment of the hadith of the bedouin). This is the view of 'Ali ibn Abi Talib, 'Omar, and ibn 'Omar, ibn al-Mubarak and a-Shafi'i and the most prominent view of Ahmad,
However Malik, al-Laith ibn Sa'ad and al-Awza'ay said two witnesses are necessary to declare the beginning of Ramadan. Based on the hadith from sunan an-Nasa'i. This aparently was also the view of 'Othman ibn 'Affan and Isahaaq ibn Rhawayh.
Abu Hanifa allowed one witness in case that the sky was obscured, else he would insist on two witnesses.
For the end of Ramadan with the exception of abu Thawr all scholars say it needs two witnesses.
This article might also be relevant.