And he that was pure, would become impure through that’Azazel.
And thus also, regarding the ‘waters of nidah’: the priest would purify her, and would be himself impure until evening time, and then would become purified.
And furthermore: on the idea of ‘it purifies the impure’. When Moses was born, it is stated of him in relation to the daughter of Pharaoh: (Ex. 2:2)... and she saw him that he was good... – for she saw the Shekhinah with him, and as soon as she touched him, she became purified and healedxxxiiSee Pirqei d-Rabbi Eli’ezer Ch.47 from her leprosy, and the leprosy then adhered to Moses, as it says: (Ex. 4:6)... and behold his hand was leprous like snow.