In the purification process for the metzora, there were two birds, one that’s left alive and is cast out on the field; the other is killed. The bird that dies, its blood is meant to drip into a pool of clear water in an earthenware vessel, changing the color of the water into blood. As part of the purification procedure, the Cohen takes a little piece of Cedar wood, a scarlet thread, and a plant called hyssop. In the purification procedure, you are supposed to take these three things and drip them in the blood of the dead bird. At the end of this purification process, the metzora can come back to the camp, but he still has to wait outside his home for seven whole days.
At the conclusion of The metzorah’s [spiritual leper] period of impurity, he must bring both a guilt offering (korban asham) and a sin offering (korban chatas). Both of these sacrifices provide atonement. Why are these two different offerings both necessary for his atonement? Usually, either an asham or chatas is required, but not both.
The Ramba”n found the double requirement of asham AND chatas by a metzorah to be noteworthy. The Ramba”n suggests that the two offerings atone for different aspects of the sin. The asham atones for the original sin that the metzorah committed which caused him to receive the Divine Punishment of leprosy in the first place. The sin offering, on the other hand, may be for sins he committed while he was already a metzorah. Maybe in his pain, he blasphemed G-d or complained about His punishment. Those complaints require independent atonement
Birds are used as part of the sacrifice\purification ritual. The reason is to remind the inflicted, do you know why you contracted the disease of tzara’at? You chattered too much! Regard this bird that constantly twitters (no pun intended)! Didn’t you act like a thoughtless twittering bird?
When one’s house is suspect of tzara’at, he has to go to the Kohen so to come and inspect it. The sages ask, what if the Kohen’s house himself is suspect? Can he check it himself? The Kohen is instructed to bring another Kohen to check, because he cannot check his own property, even though he’s an expert. The same applies to our lives. We are unable able to apply self-improvement without the advice of others because no matter how intelligent one may be, man is unaware of his own deficiencies.
Zav- If a man has an issue from his reproductive organs, he becomes TAMEY-impure and defiles others. If the issue occurred twice, it was termed “zius”, nd he immersed himself in a live or well for purification. If the ZIVUS occurred three times, during the existence of the Bet Hamikdash-Temple he counted seven clean days after the sickness ended and immersed himself in a spring or well. On the eighth day, he offered a sacrifice termed ” korban hazav” consisting of two turtledoves or two pigeons, one offered as a chatat and the other as an olah sacrifice.
The laws of nidah are very important and are the foundation of building a Jewish home. The term nidah denotes separation or aloofness. A woman becomes a nidah through menstruation, childbirth, or uterine bleeding. She thereby becomes tamay (ritually impure) and must count seven clean days and immerse herself in a mikvah in order to become purified. The husbad is commanded to separate from his wife while she is a nidah.
The forty sa’a , which constitutes the minimum volume of a mikva, hints to a person that he must purify himself on a duel level, spiritually as much as physically. The number forty alludes to the physical creation of man (since according to our Sages, the embryo’s formation takes forty days) and to spiritual renewal (since the Tablets were handed to Moshe after a forty day stay in Heaven)
credit to Rabbi Avi Matmon