The World Federation One Stop Fiqh

Ruling 1125

One must reply to salām in a manner that the person who said salām to him hears the reply. However, if the person who said salām is deaf or passes by quickly having said salām, in the event that it is possible to make that person aware of the reply by indicating and suchlike, it is necessary to do so. In other cases – except during prayers – it is not necessary to reply, and during prayers it is not permitted.