According to the Torah, the process of purifying a Metzora, one who has been afflicted with Tzoraas, involves taking two live birds and following a detailed process with each of them )ויקרא י"ד:ד'-ז'(. According to Chazal, this process, because of its symbolism, shows the Metzora how to get spiritual purification for his sin of Lashon Hora which Chazal say is the cause of Tzoraas. The chattering birds symbolized that the Metzora sinned by chattering too much Lashon Hora. The first step of the Metzora's purification is the recognition, by seeing the birds, of what the cause of this situation was. Then the Kohein had one bird killed, which showed that if one speaks too much Lashon Hora, he deserves to get killed for what he has done to destroy the life of another person. The Kohein would then take the one bird which was not killed and would let it go free. This shows the Metzora that he must continue with a regular life. After the Metzora has been punished and then recovers, his life must continue like normal, since he has been purified. Finally, before letting the bird free, the Kohein dipped it in blood, which makes a permanent stain, in order to symbolize to the Metzora that he must always remember his sin and never do it again. We thus see how this simple procedure with the birds symbolized much about the Metzora himself.