What is the ruling regarding the Friday Imam whose sermon was interrupted by a siren, causing everyone to leave: should he complete his sermon and prayer, or discontinue them?

The Imam is not required to continue the sermon if he remains alone because its purpose is to be heard by the people. If they return soon, he builds upon his sermon. However, if the interruption is long, he must resume the sermon anew. Even if others come, he must resume the sermon. If they do not return and time becomes short, he prays Dhuhr, as continuity in the sermon is obligatory, hence resuming it is necessary.