If the Lord gave the Jewish people anything, he gave them laws of cleanliness which were detailed and legion. We embarked on the beginning of those laws in chapter 12 and now we continue in 13 and beyond with the laws dealing with leprosy. Keep in mind this term in the Hebrew is not the distinct and only disease that we consider as being leprosy, but rather it is in the Hebrew a term for several skin diseases, and the precise meaning is a bit unclear.
So 13 gives the details on what to look for and what is unclean and what is eventually clean. Notice that there is a time of quarantine for those that potentially had the disease. We should feel right at home with that. More leprous descriptions take over 14 and which include not only the person but also his house and what types of sacrifices need to be done in order to come out of the leprous situation.
We then more from leprosy to the wonderful world of bodily discharges and how long a person is unclean after a discharge and how to get back into the clean world once all that business is done. We then get to the yearly ritual of atonement which involves a bull and two goats. One of the goats is said to be the one of Azazel which in Hebrew is thought to mean scapegoat. This goat has fascinated me. Every year the priest lays his hands on this goat and puts on this goat all of the sin, iniquities, and trespasses of the people of Israel and then sent off into the wilderness for all eternity. This is how the people of Israel were made clean year after year, and it had to happen year after year. This is where Hebrews tells us that with Jesus and his sacrifice, it only had to happen once, and that was enough.
In Hebrews we see the reference again to Melchizedek who is quite a secondary figure in Scripture but who is made primary by the author as Jesus has become his type. While Jesus was not from the line of Aaron he has right over this new priesthood just as Melchizedek had a right and with the changing of the family of priests there is also a changing of the covenant. He uses the words of Jeremiah 31 to describe that new covenant in chapter 8 and to underscore that as the old covenant becomes obsolete it will disappear and the new covenant, in Christ, is what will take its place.