EXILE IS A PUNISHMENT FOR HAVING LEPROUSY

Midrash Rabbah - Numbers 7:3

THAT THEY SEND OUT OF THE CAMP EVERY LEPER, etc. You find that just as a mortal king has army chiefs, so God has army chiefs; as it says, Take ye the sum of all the congregation of the children of Israel, etc. (Numbers 1:2).

A mortal king has of exile for those condemned to banishment, and God also has a place of exile for those condemned to banishment; as it says, THAT THEY SEND OUT OF THE CAMP EVERY LEPER, etc. (Numbers 5:2)