Is it sufficient to pour water to purify the spot on the body that was touched by dry istinja’ water, or is rubbing necessary?

The water that splatters during istinja’ (cleaning oneself after defecation or urination) is originally pure unless it changes due to impurity, in which case whatever of it touches the body must be purified. Doubt about the water becoming impure cancels out the impurity, because the default state is purity. If it does become impure, it is sufficient to pour water over the affected area to purify it, without rubbing or squeezing. The important thing is to immerse the impurity with water and for the water to overcome it.