These words are a literal quotation from the LXX translation of Leviticus 19:2. In three other places this same command to be holy is found in Leviticus with slight variation (Leviticus 11:44; Leviticus 20:7, Leviticus 20:26). All four of these are in the section of the book of Leviticus where the Lord gave his redeemed people (recipients of his grace as spelled out in the sacrifices of Leviticus 1:1 – 10:20) instructions about their identity as different from the peoples around them. God used instruction embedded in foods, childbirth, skin and mildew impurities, bodily discharges, and unlawful sexual relations to impress upon his people that being holy was real and visible and consequential, to the point of being strangers, oddballs in their wider society. Clearly, as foods and birthing and impurities and discharges impacted all Israel did 24/7, so the exiles’ holiness was to be 24/7, that is, “in all your conduct.”
16 since it is written, “You shall be holy, for I am holy.”