Metzora 

מצורע

When the leprosy was no longer present on the person’s body, a purification ritual involving two birds, various types of plants, and additional items was conducted. The Sages explain the connection between the components of the ritual and the actions of the leper. 

“This shall be the law of the leper on the day of his purification” (Leviticus 14:2). With what is he purified? He is purified with “two living pure birds, and cedar wood, and scarlet wool, and hyssop” (14:4). Why is his offering different from all the other offerings? Since he spoke slander, therefore the verse says that his offering includes “birds,” whose voices are heard at a distance…. “And cedar wood.” There is no tree taller than the cedar. Because the slanderer elevated himself like a cedar, he was afflicted with leprosy, as Rabbi Shimon ben Elazar said: Leprosy comes due to haughtiness…. “And hyssop.” There are no trees lower than the hyssop. Because he humbled himself [by isolating himself from society while he was a leper], therefore he is cured by means of hyssop. “And one shall slaughter the one bird” (Leviticus 14:5). Why does one slaughter one bird and send one bird away to fly away freely? It is because [the Torah is teaching the leper]: If you repent, you will not experience leprosy again; but if you do not repent, the leprosy will return to you, just as the living bird could return. 