ANSWER:

We wash our private parts only after answering the call of nature! 

Washing it before making wudhu is the doing of the shia and it is an innovation. 

QUESTION: Am I obliged to clean my backside with water if I don’t see any impurities on my underpants before prayer, can I just do wudu and read namaz?

Ablution (Wudhu), Innovations, Purity |