The fourth aliyah covers the seventh aliyah of Parsha Tazria and the first two aliyot of Parsha Metzorah. It contains the elaborate procedure to be used by the Kohain to purify the one who has tzoraas (the metzorah) from this condition.
In passuk 9, it states: "He shall shave off all his hair -- his head, his beard, and his eyebrows." The commentary Klai Yakar points out that the plagues that are mentioned in this week's Torah portions came as punishment for three things: haughtiness, gossip, and jealousy. Therefore, the cleansing process for one afflicted with tzoraas was done in the following order: First, the hair on the head was shaved off, because the person's excessive pride caused him to desire to be above others. Second, the hair of the beard was removed, because he did not control his mouth and spoke slanderously against his fellow man. Third, the eyebrows were shaved off, as they did not prevent his eyes from looking with greed at the possessions of others.