SUPPLICATING IN THE SHOWER
Q. Du`a’ while in the shower.
Normally, a bathroom is not a place of supplication, i.e. a location where one makes the intention to visit and perform intentional pleas and supplications and neither is it a place where the required mood of reverence and humility for that is induced. Nevertheless, if one happens to consult their conscience while in the shower by silently re-examining h/her own failings and wrongdoings, then there would be no harm in this. However, if one begins to make audible supplications then as long as the place is clean (free from impurities and the bathroom is not immediately adjacent to the toilet) and one’s `awra (nakedness) is covered, then strictly speaking it would not be unlawful but perhaps better avoided.
And Allah knows best.
 See Mufti Ludhianvi, Ahsan al-Fatawa, vol.2, p.36.