The Old Testament was very peculiar about unclean things, that could make people unclean. Jesus is not looking anymore at what can be washed by water and fixed by doctors or priests. Jesus is looking at a dirt that can be only washed by Him, by His Blood. Sin means death, and it is much worse than any unclean thing. The roots of sin are within, in our mind and heart. And yet, only Jesus can cure those places and make us clean again. But the time for healing is now.