[gamblingstats]

Asalamualaikum

In some mosques the Iman finishes the khutbah with a du'a and the people all recite ameen after each supplication is made.
The sunnah teaches us that it is the duty of the muslim to keep entirely quiet during the entire sermon until the end.

Where does this practice come from?
Are their any hadiths or known accounts where reciting a du'a in unison or even the imam ending in one is from the way of our predecessors?
If not then why is this a common practice we see throughout much of our land?

[Immusaatmonna]

In hanafi madhab one is supposed to be silent during the khutubah. I m not sure about the dua.

In shafi'i madhab one also has to silent during the khutbah, but can say salaath loudly when the Prophet's name is mentioned. Also dua is permitted after the 2nd khutbah before salah.