Is it permissible for someone who has confirmed the sighting of the Shawwal crescent to lead the Eid al-Fitr prayer for a congregation that relies on astronomical calculations and will break their fast one day after the crescent sighting, or should he only pray with those who rely on sighting? And is it permissible to lead the Eid prayer on two different days, depending on the differing determination of the Eid day among Muslim groups?

It is imperative to strive for unity of word and cohesion of ranks, and for this unity to be in accordance with the dictates of the Shariah proofs, by clarifying that what is considered valid for the sighting of the crescent is the legal sighting through the testimony of righteous witnesses, and there is no room for the calculations of calculators in this matter.

If it is established for you by sighting that the month has ended and that the day is Eid, then it is obligatory for you to act according to what the sighting indicates. So, you should pray Eid with those who pray on that day. As for your prayer on the morrow with those who act according to calculations, we do not approve of this for you, as it involves acknowledging their reliance on calculations, which is Islamically invalid.

However, if your refraining from praying with them leads to a predominant harm, then it is permissible for you to pray with them. In this case, your prayer will be a supererogatory act and an additional good deed, as stated by Ash-Shafi'i regarding someone who sighted the crescent alone, or a group who sighted the crescent but their testimony was not accepted. Such a person or group should secretly break their fast and pray Eid alone, then on the morrow, go out and pray Eid with the people.

When this harm is not present, then you should pray Eid on the day it is established by sighting, and do not pay attention to the opinion of those who differ and act according to calculations.