Does a small amount of urine impurity become pure if it dries on the body, or must it be washed off?

The drying of impurity and the disappearance of its trace does not purify the locale. This is the view of the majority of scholars, who hold that it must be washed.

As for a small amount of impurity, there is a difference of opinion among scholars regarding it. The majority holds that nothing among impurities is excused except for a small amount of blood and pus, because the proofs do not differentiate between a large and small amount of impurity.