Assalamu Alaikum Wa Rahmatullah,
My local masjid is barelwi-oriented and after every fard salah, the Imam would say ''Afdalul-zikr" and all of them would say la-ilaha-illa-Allah loudly together (the tune's quite catchy actually ). I never join them and just do my dhikr quietly (e.g. 33 SubhanAllah 33 Alhamdulillah...........)
So far, as per my knowledge permits and what others have told me, this practice appears to have no basis in the Sunnah. Can anyone confirm this? Is there some ahadith that shows this was practiced?