“And the person being purified must wash his clothes. And he shall shave off his hair. And he shall immerse in water and be pure. After he shall come to the camp. And he shall dwell outside of his tent seven days.” (VaYikra 14:8)
The pasuk explains a portion of the purification process for an individual who is afflicted with tzara’at. The process includes immersion in a mikveh.
Sefer HaChinuch discusses the function of this immersion. He explains that immersion represents a rebirth.  Why is this symbolic rebirth needed?
Our behaviors are influenced by our perception of ourselves. A person with a poor self-image will usually conduct his or her affairs in a manner consistent with this image. A sinful person cannot alter behaviors without a change in self-image. This is the most difficult aspect of repentance. Appreciating the error of sin is only a first step. Even sincere regret cannot have a lasting effect upon future conduct. A drastic long-term change in behavior requires the establishment of a new identify. Only if this new image is developed, will long-term change be assured.
Immersion in the mikveh symbolizes this concept. The truly repentant individual must break away from the previous self-image. A rebirth must take place. Only with the establishment of a new self can the repentant individual succeed.
“And the Kohen shall command that the house should be emptied before the Kohen comes to view the affliction. And everything in the house shall not become unclean. And after this the Kohen shall come to see the house.” (VaYikra 14:36)
The Chumash explains that tzara’at is not only an affliction of the body. Tzara’at can also appear as a discoloration of a garment. A house can also be afflicted by tzara’at. Obviously, the tzara’at that appears upon houses and garments is not the same physical condition affecting the body. The Torah uses the same term for all three afflictions. This is not intended to imply that the three phenomena are identical. The common term reflects that all three conditions are related.
Our pasuk discusses tzara’at of the house. The Torah explains that before the Kohen evaluates the house it is emptied of possessions. If the Kohen identifies the discoloration as tzara’at, all the items in the house will become unclean. Rashi explains that this is the reason for removing the possessions. The Torah is demonstrating compassion for the material well-being of the owner.
Sforno understands this issue differently. The Torah instructs the Kohen to delay his arrival. The Kohen should not view the home until the possessions are removed. This creates a delay. First, the owner suspects that the home may have tzara’at and the Kohen is summoned. Then this delay occurs. After the delay, the Kohen arrives and makes his pronouncement.
What is the purpose of the delay? Sforno explains that this period offers the owner the opportunity to repent. As the owner removes all possessions from the home, there is an opportunity to consider the implications of the events occurring. This will, hopefully, encourage the owner to reassess his or her behavior.
“If a woman has a discharge of blood that emerges from her body, seven days she shall be ritually unclean because of her menstruation. And anyone touching her shall be unclean until evening.” (VaYikra 15:19)
This pasuk introduces the law of the nidah. A woman, during the period of menstruation, becomes ritually unclean for seven days. During this time marital relations are prohibited.
Marriage involves a lifelong partnership between husband and wife. This is a wonderful relationship. The Almighty did not create the human to live in solitude. The marital partnership is essential to human happiness. However, marriage presents challenges for both partners. It requires compromise predicated upon mutual love and affection. The emotions flowing between husband and wife bind the partners together as a unit.
Inevitably, with the passage of time, familiarity develops. With familiarity the intensity of the feeling shared by husband and wife can dissipate. This can be disastrous. Without these feelings, it is difficult for to individuals to spend their lives together. The motivation to resolve marital conflicts and reach compromises falters. With familiarity, intimate relations, between husband and wife, become less exciting. Intimacy may become replaced by boredom or disillusionment.
How can the long-term nature of the marital relationship be reconciled with the danger of familiarity? Sefer HaChinuch explains that the law of nidah responds to this conflict. Through observing this command, husband and wife forgo intimacy for a portion of each month. This abstention helps foster renewed appreciation and desire. When the nidah period ends the couple is fully reunited. The reunion rekindles the intense feelings between husband and wife. Marriage and mutual appreciation coexist.
 Rav Ahron HaLeyve, Sefer HaChinuch, Mitzvah 173.  Rabbaynu Moshe ben Maimon (Rambam / Maimonides) Mishne Torah, Hilchot Tumat Tzara’at, 16:10.  Rabbaynu Shlomo ben Yitzchak (Rashi), Commentary on Sefer VaYikra 14:37.  Rabbaynu Ovadia Sforno, Commentary on Sefer VaYikra 14:37.