Bismillahi -rrahmani-rraheem, Assalamualaikum, When I go to the toilet to defeacate, it happens that the water inside the toilet sit(it will contain my urine) splash on different parts my body.So at the end I can't really pinpoint where exactly it splashed so I wash every part of my body trying to make the sponge actually pass over all parts. But this turns out to be rather time consuming.For example if one rubs the sponge liberally on the thighs or the trunk,then some parts may be left untouched by the sponge.Can one just say: well those parts are already touched by water and probably, any urine that has dried on the skin will have been dissolved ? Thank you.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

We have already issued Fatwa 92641 clarifying that it is an obligation to wash the impurity which splashes on the body when relieving oneself, provided that one is sure or pretty sure that an impurity touched his body.

Therefore, if you are sure or predominantly believe that an impurity touched a part of your body when relieving yourself, then you are obliged to wash that place.

There is no doubt that washing the entire body in such a case is considered a dispraised whispering, because there is no need for one to wash the chest, the stomach, the neck, and the feet just because of the impurity touching the surroundings of one's private parts. Therefore, you should be careful of the whispers of satan as it is an evil that could turn a person mad. 

For more benefit on how to treat whispers, please refer to Fataawa 92050 and 84603.