In this chapter, the LORD prohibits a variety of sexual relations and child sacrifice, which were performed by the nations of the promised land.
This chapter marks a shift in the tone of Leviticus, as the focus drifts away from the sacrificial system and laws of ceremonial cleanliness and towards the general governance of behavior (not just of the priests, but of the whole people). Governance of general behavior was definitely the subject of earlier Exodus passages related to the covenant (Ex 20-24), but it's new to Leviticus. Just as before in Exodus, this behavior (in this chapter, immoral sexual relations) does not have any overt religious significance, but since it is part of the covenant, that ascribes it a sort of implied religious significance, which is emphasized at the end of the chapter.
The beginning of the chapter reinforces the principle of separation, which is the justification for these moral laws. Indeed, I hypothesize these are moral laws and not ceremonial. As I said before, I hypothesize that ceremonial laws are principally related to ritual purity, which has to do with tabernacle worship and socially isolating disease. The term "unclean" or "impure" does not appear in this chapter, suggesting a transition from the ceremonial code to a section of moral code. The new word describing these acts is much stronger, "abomination" (NASB, Hebrew "toebah", meaning "disgusting", an "abhorrence", often idolatry, "abomination"). Committing an "abomination" is not something that a ritual washing can fix; as verses 25 tells us, these abominations defiled the land, so "the land has spewed out its inhabitants" as a result.
Given that this is the book of the priesthood, it's a bit confusing that it contains a section on moral code that doesn't particularly have to do with the priests. All I can say is, welcome to the OT. The author does as he pleases around here, and if he wants a moral section in the Levitical code, then that's where it shall be! Regardless, this section is relatively short and going forward, there is a mixture of what people call the Holiness Code and more regulations of the priesthood, and we just have to deal with it. Fortunately, it's usually easy to separate the two types of discourse and analyze them in turn.
This chapter, as we can see, is primarily focused on prohibiting sexual relations between close family members, a prohibition that is still broadly enforced today, though the details probably vary between the biblical laws here and modern law. The underlying principle is to prevent genetic defects. Without going into a full-blown biology lesson, people have "recessive genes" which are only expressed in a person if both their mother and father carry that recessive gene and both parents transmit that gene to their child. There are many types of recessive genes, and not everyone has all of them. Some are quite rare, and when expressed, can cause a deformity or harmful mutation. Since people within a family are substantially more likely to carry the same set of recessive genes, if two people from the same family marry and have children, it dramatically increases the likelihood that any recessive genes in the family will be expressed in the children, resulting in harmful mutations. Not all recessive genes are harmful of course, but some are.
It's a statistics thing, so there's really no guarantee that incest will result in genetic deformities, and there's no guarantee that marrying outside your family prevents it, but incest heightens the risk of such deformities tremendously. I think that's the main reason why these kinds of laws are still in effect today, and we can hypothesize (but not prove) that it's the reason why these laws are effected by Leviticus in our current chapter.
Verse 18 directly outlaws what Jacob (one could argue unintentionally) did with Leah and Rachel, marry a woman and her sister. The life of Jacob and the many struggles that emerged between Leah and Rachel are a great example of why this is banned here, that it creates a rivalry between the two sisters.
Furthermore, Gen 20:12 suggests that Sarah was Abraham's half-sister, which means their marriage was also a violation of the laws in this chapter.
As I have previously noted, the patriarchs were not bound by the Mosaic covenant, so they didn't technically do anything wrong. I wrote that in the context of Abraham's association with Mamre the Amorite, which is also generally prohibited under the principle of separation. I also think these three things (association with Mamre, marriage between Abraham and Sarah, marriage between Jacob and Leah/Rachel) are pretty good examples of things that the bible is against, yet does not explicitly condemn. In fact, many readers probably wouldn't even know that the bible were against these things if they only read Genesis and did not continue on to the rest of the Pentateuch. So the bible will not always tell us the moral judgment of an act when it happens, and this has important implications in many places.
We also see a reference to people sacrificing their children to Molech. Molech is the Hebrew word for "king", so some translations have more references to Molech than others. In the OT, Molech (the false god) is usually associated with child sacrifice, as we find here, and the idea is that Molech would bless you (the parents) for killing your child in this way. Some Christian authors suggest that child sacrifice to Molech is a moral precursor to abortion, in the (presumptive) sense that an abortion is performed for the sake of money or convenience on the part of the aborting woman. As such, this is a reason why some Christians oppose abortion. This verse is strangely placed in a chapter about unlawful sexual relations, which suggests that this chapter is more focused on the principle of separation by not following other nations' customs, rather than on sexual relations for its own sake.
I find it strange that there is a prohibition against sex with a woman during her menstrual period when just previously in Lev 15:24 there is a ceremonial provision made for the case when men do this. I don't understand why there is a need for a ceremonial provision if the action is morally prohibited.
Finally, we reach a prohibition on male same-sex intercourse. By most interpretations, verse 22 says "You shall not lie with a man as with a woman; it is an abomination." (Amplified). I've heard some people challenge this translation, but the majority of scholarship seems to support it, as well as every bible translation I have read so far. After investigating for some time, I am pretty convinced this is the correct translation. One can distinguish between the correct translation and the proper interpretation, however, so additional study is warranted.
There is a more significant question of whether this verse also prohibits female same-sex relations, and I think the answer is no. From a literal rendering, it is clear that this is governing male behavior and not female behavior. However, my understanding is that female same-sex relations were much less common, if practiced at all, in the time frame of this document. On the other hand, while lesbianism is not banned here, there is a Midrashic tradition that it is implicitly banned in 18:3, under the presumption that lesbianism was practiced in Egypt and is one of their "practices" which the Israelites must not follow.
I'd also like to take this opportunity to raise a meta-comment here, that despite the frequency of discussing homosexuality and the bible in popular culture, the subject forms a fairly insignificant fraction of the actual biblical text. To wit, consider that we are now 109 chapters into the bible and this is the second passage that is generally construed as a condemnation of homosexuality (possibly third if you count Genesis 2), and in this case it's literally just one verse in the midst of a whole chapter that covers other, albeit related, topics. I think that many people have the unfortunate misperception that homosexuality/gay marriage and abortion (the two big social issues in America at present) are "what the bible is all about", which is just blatantly false. From my perspective, this has the somewhat humorous result that I spend almost no time reading or thinking about homosexuality in the bible, and yet that's what many non-Christians ask about. In the end, I have studied the issue at depth to ensure I have a good answer to the social questions, but as it relates to the biblical narrative, it is simply not that big a deal.
Still, how one approaches the issues of homosexuality and gay marriage in the bible has significant import as it relates to one's biblical hermeneutics (i.e. system of interpretation). That is, suppose you take a verse like Lev 18:22 and say, "the OT is not relevant to our day". It might not make a big difference to disregard this single verse, and yet the particular reasoning for discarding Lev 18:22, that the OT is not relevant, is a very significant decision in its own right, because to be logically consistent, one must also discard the rest of the OT.
That's what makes the issue of homosexuality in the bible a litmus test of sorts, because while it may be insignificant compared to the sacrificial system, etc, the way a person approaches this issue is generally representative of how they approach the many more important issues in the bible, because most people use the same hermeneutical system across those many issues. Generally, conservative readers wish to maintain a prohibition on homosexuality because of an idea about the sanctity of the bible, that it doesn't matter how brief a command might be, that the prohibition of homosexuality is part of the bible and as such, it must not be disregarded no matter what. Progressives, on the other hand, often point to historical examples of wrongs justified by biblical argument. The best example of that is the argument for slavery on the basis of the "curse of Ham" (Gen 9). This is a biblical argument that was eventually overturned as slavery was itself abolished, and liberals see the prohibition of homosexuality to be another biblical argument that will fall with the advent of societal change.
Personally, I have a lot of sympathy for the conservative argument, because I too wish to honor the sanctity of the bible. Yet, I also feel that conservatives should seek to guard themselves from the mistakes of the past, using a false biblical argument to justify a social position. Conservatives will (and do) say that the prohibition of homosexuality is clear as day, irrefutable, and that progressives wish to simply discard biblical morality and engender moral relativism (a curse word in many conservative circles). Yet, as my readers will learn, the more we progress into the issues of biblical hermeneutics, the more we will discover it is a deeply complex subject. Even with my discussion of moral law vs. ceremonial law (which has tremendous implications going into the NT), there does not seem to be a clear separation between the two, just as the ceremonial law of Lev 16 merges into the priestly moral law of Lev 17, which in turn merges into the general moral law of Lev 18. With the author flowing freely through these subjects, our dissection of them becomes that much more complicated and error-prone. So much of how people understand the bible comes not from the text itself, but from our assumptions and preconceptions before we open the book, and that's why I was careful to state my own preconceptions back in the prologue.
For this reason, there are many progressive Christians who support gay rights and think they honor the bible as well, because they simply interpret verses like Lev 18:22 in light of different preconceptions than the conservative.
For right now, I cannot state my own position on homosexuality and gay marriage without speaking in light of the NT, and so I must defer for now. Even if I were to state my opinion, I would encourage my readers to study the subject and form their own opinions, because that's the purpose of this commentary. Furthermore, I would encourage my readers to pray about the issue and seek divine guidance, because ultimately what we are seeking is God's law and God's judgment of the matter, that we might do what is right rather than blindly follow the cultural traditions that have been set before us, whether conservative or progressive.
What I will say is that verse 22 is an authoritative condemnation of homosexuality that would almost certainly have been upheld in ancient Israel. We have centuries of rabbinical and Christian traditions that interpret this verse as such. Like most of the sexual laws, it would have probably been punishable by death, and like most sexual laws, there are probably very few people who would have been killed for it, because the death penalty in Israel requires two witnesses, and by their nature sexual acts are usually not witnessed by anyone beyond their participants. Nevertheless, the condemnation is significant because it is a moral judgment, apart from any punishment, and it sets the boundaries of acceptable behavior which are taught to the people. My understanding is that Orthodox Judaism still holds that homosexual acts are wrong, based on verses such as this. The big question is whether this condemnation holds through the NT, and that's something I will address when we reach the NT.