Is the earth pure, and is it permissible to measure the purity of sandals by rubbing them, analogous to a car tire that passes over sewers?

The earth does not purify impurities; rather, pure water purifies them. However, some traces of impurity may be excused, and car tires are purified if they become contaminated with impurity and are rubbed until its trace disappears by driving, by analogy with shoes. Some scholars are of the view that shoes are purified by rubbing them on the ground, whether wet or dry. This is the opinion of Al-Awza'i, Abu Hanifa, Abu Yusuf, the Zahiris, Abu Thawr, Ishaq, and Ahmad in one narration, and one of the two narrations from Al-Shafi'i.