13:1–14:57 These chapters contain God’s laws concerning unclean skin diseases referred to as “leprous disease” (13:2, 8). Modern physicians recognize here the symptoms of various modern complaints, but we should remember that the biblical classification is based primarily on spiritual rather than hygienic or medical considerations. The key principle in identifying a skin disease as “unclean” was whether the skin seemed to be rotting away, suggesting the spiritual principle of death. Patchy complaints amounted to uncleanness (vv. 9, 10), but a complaint affecting the whole body did not (vv. 12, 13). Stable conditions were clean, but deteriorating ones were unclean (vv. 5–8, 18–37). Similar principles applied to the diagnosis of uncleanness in clothing: progressive mildews were unclean (vv. 47–52), but stable ones were clean (vv. 53–58). The close association of uncleanness with death is shown in 13:45. The person afflicted with a serious skin disease behaved as a mourner (21:10). He was excluded from the camp, not to protect the health of Israel, but because God was in the camp and uncleanness (death) had to be separated from the presence of God (life). See Num. 5:1–4; 12:14–15.