What is the ruling on unifying the Adhan (call to prayer) within a single country, with mention of the evidence?

There is no objection to unifying the adhan (definition) (call to prayer) audibly within a single city if the time for the beginning of prayer is uniform. However, if the time for the beginning of prayer differs in various locations within a vast country, then unifying the adhan is not permissible. This is because it could lead to prohibited outcomes, such as calling the adhan before the proper time, which might cause a fasting person to break their fast before sunset or lead to performing the prayer before its prescribed time. Conversely, delaying the adhan could lead to eating the suhoor (definition) meal after dawn.

Jurists have unanimously agreed on the impermissibility of calling the adhan before its due time, with the exception of the dawn (Fajr) adhan. It is sunnah (definition) (recommended) to call the adhan at the very beginning of the prayer's time.

As for delaying the adhan past the beginning of its time, it should not be done, unless there is a necessity and it does not cause confusion. The sunnah is to call it at the beginning of the time.