What is the ruling on repeating the Fajr prayer (both its obligatory and supererogatory parts) individually, after having performed it in congregation, on the pretext that the congregation prayed at an incorrect time, knowing that this is based on a mere assumption or unsubstantiated claim, and not on sound religious knowledge?

The time for Fajr prayer begins with the appearance of true dawn and ends at sunrise. The prayer is not valid unless one is certain that the time has begun or has a strong presumption of it. One should not doubt the usual prayer time for the congregation based on an unknown or unreliable source, and it is not permissible to repeat a prayer after it has been performed on time without a legitimate Shar'i reason. An ordinary person should ask trustworthy scholars about religious matters, as Allah Almighty says: "So ask the people of the message if you do not know." It is advisable to strive for unity and to refer disputes back to the Quran and Sunnah (definition).