Or HaChaim on Leviticus 20:26/אור החיים על ויקרא כ׳:כ״ו

1 והייתם לי קדושים, "And you shall be holy unto Me, etc." The reason the Torah adds the word לי in this verse may best be understood in connection with the comment of Torat Kohanim on this verse that one should never say: "I cannot eat pig's meat," but one should say: "I would love to eat pig's meat but alas, G'd has forbidden it to me." Similarly in our verse G'd does not want us to be holy because we detest the various phenomena in this world G'd has prohibited to us, but He wants us to be holy because He has commanded us to be so, i.e. לי. This is also the reason this verse appears next to the commandment to separate between the ritually pure and the ritually impure mammals and fowl (verse 25).

2The Torah added: כי קדוש אני, "for I am holy," to tell us the reason we must keep our distance from the impure creatures. G'd continues to explain this concept of separation. He has separated us from the Gentiles; it is no more than fitting then that we separate ourselves from the impure species. We have reason to bless the Lord for having set us apart from both human and animal impurity.