The disease of tzara’at came about through malicious talk, which the Talmud compares to the mindless chattering of birds. Therefore purification ritual from tzara’at requires birds to be effective (Arachin 16b). But why is one bird killed and the other set free? The Sefat Emet offers a profound insight in his commentary on this parasha. The birds are there to atone for two sins. The one that is slaughtered is there so that one will cut himself off from idle chatter, and much more from evil talk itself.