Is a small amount of severe impurity excused if it gets on a shoe or a foot, and is the inside of the foot and the shoe that steps on impurities purified by coming into contact with pure ground?

A small amount of severe impurity thataffects the bottom of a khuff (leather sock), shoe, or sandal is excused if it is rubbed on the ground until the impurity itself is removed. This is the view of the Hanbalis, Al-Awza'i, and Ishaq. They cite as evidence the hadith of Abu Hurayrah: "If one of you steps on filth with his khuff, their purification is dust." They also cite the prayers of the Prophet (peace and blessings be upon him) and his companions in their sandals. There is no difference between dry and wet impurity regarding the sufficiency of rubbing it off. However, this exemption does not apply to impurities that affect the human body; rather, they must be washed with water and the impurity removed.