the ḥadith of Ibn ʿUmar, may Allah be pleased with him, in which the Messenger of Allah (blessings and peace be upon him) said: “Do not begin the fast until you sight the crescent, and do not break the fast until you sight it; if it is obscured from you, then calculate for it.” Recorded by al-Bukhārī and Muslim in their Ṣaḥīḥ collections.
This ḥadith makes the ruling contingent upon its cause, namely actual sighting. The moon may be sighted in one place—such as Mecca or Medina—yet not be seen in another, and at that very moment it may still be daytime for people elsewhere. How, then, could they be instructed either to fast or to break the fast? This point has been clarified in Bayān al-Adillah fī Ithbāt al-Ahillah.
The scholars of every legal school have therefore affirmed that the criterion is the difference of horizons. Ibn ʿAbd al-Barr even transmitted a consensus that a moon-sighting in widely separated regions—such as Khurāsān and al-Andalus—is not binding on each other, and that every land has its own ruling. The works of the four Sunni schools are filled with discussions affirming the legal weight of horizon-difference, supported by clear scriptural proofs; a survey of the fiqh literature will amply demonstrate this.
From the standpoint of reason, no scholar disputes the factual reality of differing horizons; it is an observable phenomenon that the intellect readily confirms. Revelation and reason thus agree, and many rulings—among them the prayer times—are built upon this principle. A look at present-day realities likewise shows the objective fact of horizon-variation.
In light of all this, the Islamic Fiqh Council has resolved that there is no need to call for a single, worldwide new-moon sighting or for unified religious festivals in the Muslim world, for such unification does not in itself guarantee the unity of the Muslim community, contrary to what many proponents imagine. The matter of confirming the crescent should instead be left to the fatwa-issuing and judicial bodies in each Muslim country, for that is more appropriate and more conducive to the overarching Islamic interest. What will truly unite the ummah and bring its word together is their collective adherence to the Book of Allah and to the Sunnah of His Messenger (blessings and peace be upon him) in all their affairs. Allah is the One who grants success.
And may Allah bless and grant peace to our Prophet Muḥammad, his family, and his Companions.