The unique laws of the metzora have established that, despite the fact that his contamination is manifested in a change on his body, it was caused by his degraded spiritual condition. Being alone outside the camp gives him the opportunity to reflect on his deficiencies and to repent so that he can once more become worthy of becoming part of his nation. As soon as that change takes place within his mind and heart, the same יהוה who afflicted him will remove the mark of his degradation and he can begin the process of return.
Leviticus 14:1 And יהוה spoke to Moses saying, 2 זֹאת This will be the Torah of the leper in the day of his cleansing: He will be brought to the priest: 3 And the priest will go outside of the camp; and the priest examines to see if the sores have healed in the afflicted person. C-MATS
Question: What are seven sins that bring on tzara’at? slander, bloodshed, false oath, incest, pride, robbery, envy
Leviticus 14:4 Then the priest will command for him who is to be cleansed to take two living clean birds and cedar wood and scarlet yarn and hyssop branch. C-MATS
Question: How does the metzora receive atonement for his sins? Atonement for sin requires that the former sinner purge himself of the moral flaw that caused his misdeeds. The underlying cause of slander and gossip — the sins that are punished by tzara’at — is haughtiness, because it breeds the contempt for others that lets one talk about them callously. The metzora’s repentance entails a resolve to change himself, a change that is graphically symbolized by the Cedarwood, Crimson thread, and Hyssop. Chumash