Is it permissible to leave the mosque if the Imam combines (prayers) without a legitimate Shar'i excuse?

Combining two prayers without a valid excuse is a grave transgression and a major sin.

The Imam who combines prayers without a valid excuse must be advised, and it should be clarified to him that his action contradicts the texts of the Sharia, as Allah Almighty says: "Indeed, prayer has been decreed upon the believers a time-bound ordinance."

It is not permissible for the congregants to follow the Imam in this combining of prayers. If the Imam does not refrain from doing so, they should pray the first prayer with him, then leave the mosque as an act of denouncing the wrong. If it is possible for them to replace the Imam with another, they should do so.