Reciting tasbihs together after congregational prayers?

In my country and some others it is custom for muazzin to lead in dhikr after finishing congregation where he says first words of tasbih loud and then all follow in low voice reciting what is customarily recited after every daily prayer. At the end imam recites dua where everyone says amin and then everyone goes by his own business. Is this bida'h sharr as some salafis and tabligis are saying or mubah i.e. permissible but not recommendable practice?

Walaikum assalam,

This is the inherited practice of the scholars of many lands where scholars are widespread. This includes Damascus, which used to be one of the great qiblas of sunni knowledge.

The scholars state, "Inherited practices cannot be innovations." (al-mutawarathu la yakunu bid`atan)

This is explained as being those widespread practices performed by successive generations of Muslims in lands where the people of knowledge were numerous (such as the great cities of Islam) and they accepted these actions.

And Allah knows best.

Walaikum assalam,
Faraz Rabbani.