Sin and God shall not dwell together. If God was to be among them, the people must put the lepers out. A leper, as is well known in Scripture, is a type of one in whom, sin is at work.
Now, sin is in all Christians, but it must not be allowed to work, and if by chance it does come out, it, must be judged and confessed to God, and given up. It may come out in different ways, and this chapter tells us this; but it is a holy God that we have to do with, and He will not go on with His people if they go on in sin.