John Lightfoot on Matthew 15:20

[With unwashen hands.] He saith not with unclean hands, but unwashen; because, as we said before, they were bound to wash, although they were not conscious that their hands were unclean. In Mark it is with common or defiled hands, Mark 7:2; which seem to be called by the Talmudists impure hands, merely because not washed. Judge from that which is said in the tract Challah: "A cake is owing out of that dough which they knead with the juice of fruits: and it is eaten with unclean hands."