Numbers 5:3

3. Without the camp We are not to suppose that these impure persons were left without shelter. Severe indeed, and inhuman, would this banishment of morally innocent persons be, if there were no provision made for their comfort. Pest-houses specially set apart for lepers outside the towns are found in Palestine to this day. Dr. Robinson mentions one opposite the Zion gate of Jerusalem. May it not be because all manner of spiritual leprosies and impurities are without the camp that we are to go forth thence bearing Christ’s reproach? Hebrews 13:13.

In the midst whereof I dwell This is the chief reason for the sanitary ceremonial and moral cleansing of the camp. It also typically enforced the practice of moral purity: “Cleansing themselves from all filthiness of the flesh and spirit.”