Moses and Aaron are instructed regarding the diagnosis of tzaraat, which is usually translated as leprosy.  It is an ailment, which has the ability of affecting human skin, clothing.  If infected, the human being or garment is declared ritually impure. Rashes, patches and discolorations of the affected individual or object are examined by a priest who determines the existence of the affliction.  

God instructs Moshe in the purification process for a leper who has been declared clean.  Two clean birds are to be brought to the priest. One is sacrificed, and the other bird is set free.  After a week, the person to be purified shave all of their hair and immerse in water. They then bring a guilt offering and a sin offering.

Rashi offers a rationale for the two birds.  Since tzaraat comes in retribution for lashon hara, which is, in effect, babbling words, the Torah requires for the metzora’s purification birds which babble and twitter continually.  But why two birds? Wouldn’t one have served the purpose? And why was one bird slaughtered and the other kept alive to be sent away “towards the fields”?  The power of speech is a double-edged sword.

When used properly it is a beneficial instrument for studying, teaching and creating community and meaning. Used improperly, in the form of slander and lying, speech can be deadly.  Our Sages explain that the sacrifices are designed to make the donor mindful of the fact that the sacrificed animal is taking his place, in reality he deserved to suffer the fate of the sacrifice.  Had there been only the slaughtered bird, the metzora would then have inferred that all forms of speech are evil and deadly.  He may not have uttered another word for the rest of his life. The live bird that is sent away toward the fields shows him that the power of speech can be a source of life and strength.  Indeed, the pair of birds epitomizes the saying that “Death and life are in the power of the tongue” (Mishlei 18:21). (Shlomo Ganzfried, author of the Kitzur Shulchan Aruch)