I notice an addition, in chapter 20, to the oft repeated phrase: “I am Adonai (your God)”. It is the clause: “who sets you apart to be holy” or “who sets you apart from other peoples”. Then, in chapter 21, comes a slight shift in the clause, indicating an even more intimate relating: “I, Adonai, who makes you holy, am holy” Leviticus 21:8b and “…I am Adonai, who makes him holy” Leviticus 21:15b.
Oh, thank you Father! You don’t just demand perfection and then leave me to work it out on my own; You set me apart and then You, Yourself, come in and make me holy!