Islamic scholars explain in this fatwa that if a mosque has a fixed and appointed imam, then starting another congregation before or after his prayer without his permission is makruh. This is the relied upon ruling mentioned in classical fiqh books such as Al-Majmu‘ Sharh al-Muhadhdhab.

However, if the mosque is located in a market or on a public pathway where people frequently come and go, then starting a new congregation is not considered makruh.

The scholars also clarify that if a mosque does not have a fixed imam, then there is no dislike in holding a second or even third congregation.

But if the mosque has a regular imam and it is not a public place with constant traffic, then according to the Shafi‘i madhhab, a second congregation without his permission is makruh.

This is the Islamic ruling given by the jurists on this issue.