In this long chapter we are told how to ritually cleanse someone restored from a skin disease and the identification and treatment of house mold.
This chapter starts off where the last one left off, by telling us how to ritually cleanse someone after they are restored from an infectious skin disease (traditionally translated "leprosy"). This ritual is conceptually similar to the cleansing sacrifices related to childbirth (Lev 12:6-8), but more extensive. There is first this ritual regarding two birds and some wood and string and hyssop (a small, flowering plant). This is a peculiar bundle of things. From the string, we would suppose that these things were meant to be tied together, and yet the text does not make this clear. I've read a few commentaries and it seems that there is no consensus whether the bird would have been tied together with the wood and hyssop.
Probably more important is that the offerer is sprinkled with blood seven times. At first glance, this reminds me of Ex 24 and the blood sealing the covenant, yet I don't believe that is the allusion made here simply because the offerer is not entering a covenant (also, the particular details vary considerably between here and Ex 24). More likely, I think we should compare this with the blood of the Passover and sacrificial atonement.
The remaining bird is let go, and most commentaries say this is symbolic of the offerer who is now "let free" to go back to the camp of the people.
After eight days (and some more ritual purification through washing), the offerer must give yet more sacrifices to finish the process. Strangely, these sacrifices resemble the consecration of the priesthood (Lev 8) more than anything else, because the offerer is supposed to have his right ear, thumb and big toe dipped in both blood and oil, just like the priests. Are we supposed to draw a connection between the two rituals? I'd say probably not, but perhaps it shows that the consecration of the priests also involved their atonement (which I think is true). I think the significance of the ear, thumb and toe is that it metaphorically ranges "from head to toe", which is an expression denoting the complete body. I.e. the priest only anoints three parts of the offerers body, but it symbolizes anointing his whole body and therefore his whole life.
The offerer is to give a guilt offering, then a sin offering and then a burnt offering, along with a grain offering and olive oil. This is a different set of offerings than the consecration of the priesthood, and it's in a different order too. This is one of the few rituals that involves a guilt offering, possibly because the infected person would generally have been ceremonially unclean for a long period of time (given the possibly long duration of such ailments). Also, the consecration of the priesthood involved a fellowship offering, whereas this ritual does not. So the ritual in this chapter seems more focused on atonement with the guilt offering, sin offering and burnt offering, while the consecration of the priesthood is more focused on bringing the priests into an agreement with God by first atoning for them and then "eating a meal with God" to secure their covenantal position. This chapter also includes a "reduced price" offering to account for economic hardship because it is an involuntary offering (i.e. if you get an infectious skin disease, you must make these offerings to be declared ritually pure and re-enter the community).
Next, we are told how the priest is to diagnose and treat mold growing on houses. Notably, the people will not have houses while wandering in the desert, so v. 34 tells us this regulation only applies when the people settle in Canaan. In general, the process for dealing with moldy houses is very similar to the treatment of moldy garments. It is inspected, quarantined, re-inspected, one attempt at a repair (removing the infected portion), and if the infection returns, it is destroyed. Just as with infectious people, this is meant to prevent the mold from spreading to neighboring houses and therefore protect the community from malignant, infectious agents.
Unlike a moldy garment, there is a sacrifice to purify the house from its uncleanness and the sacrifice is virtually identical to the first offering earlier in this chapter. Presumably the symbolic intent of the sacrifice is also the same.
One thing I found amusing about this section is v. 36 where the priest is to command "that they empty the house before the priest goes in to look at the mark". The idea is that when the priest identifies a "mark", everything inside the house becomes unclean by association. However, if your possessions are removed before the mark is identified, then they are still clean. This appears to be a hardship compromise, so that the owner of the house doesn't have to lose both their house and all their possessions (though contrary to other hardship provisions, this one is not conditional: the rich get it just as much as the poor).
Anyway, I just thought it was interesting that the possessions could be removed and remain clean because it seems that the priest declaring the house unclean is the operative factor. And it's not like they are trying to deceive the priest by removing everything before telling him: the priest is to command the owner to do this. It's a minor note, but I was amused.
And with that, we are now done with the section on communicable diseases.