Leviticus 18 Chiasm

It's been a while between chiasms, but Leviticus 18 was really asking to be analysed in this way.

A 1-2 Introductory formula - I am Yhwh your God

B 3 Don't be like Egypt from before or like Canaan in the future

C 4 Do follow my laws - I am Yhwh your God

D 5 Follow my laws and you will live - I am Yhwh

E 6-20 Don't approach your kin for sexual relations - I am Yhwh 

E' 21-27 Don't give your children to Molech and profane the name of your God - I am Yhwh

D' 28-29 Defile the land and you will be spat out and cut off

C' 30a Keep my requirements

B' 30b Don't follow detestable practices from before you

A' 30c I am Yhwh your God

I think the key to this structure is understanding what the phrase 'I am Yhwh (your God)' is doing. It seems it's generally at the end of sections. So the second half of the prohibitions (18:21-27) begins with a line about Molech and concludes with the phrase 'I am Yhwh'. This is not dissimilar to the beginning of the prohibitions in 18:6. What 18:6, 21 are doing then is acting as headings to the following prohibitions, which are distinguished in the opening and closing, as the laws for Israel (18:4, 30a) are compared with those regarding the future (18:3, 30b).

18:5, 28-29 clearly present the deuteronomistic understandings of the author (cf. Lev 27), where following God's laws will lead to life, while rejecting them will mean Israel will be spat out and cut off.

As with all of Leviticus, the reminder throughout (6x in this chapter) is that Yhwh is their God, and he is infinitely holier with infinitely higher standards that must be adhered to.