Person washing their hands before doing any work
If a kafir (disbeliever) wants to do laundry or wash our hair, do we need to ask him to wash his hands before doing that, because he will touch our hair or clothes when it’s wet?
Wa’alaykum as Salam wa rahmatullhi wa barakatuhu,
If you cannot clearly see any impurity on the hands of a believer or disbeliever, nor are you aware of their hands being impure, there would be no need to request them to wash their hands. Rather, we will assume their hands to be clean.
There is no need to have any waswasah (doubt) with regards to the purity of the item which they washed.