1-peter 1:16

Because it is written, Be ye holy; for I am holy - Leviticus 11:44. This command was addressed at first to the Israelites, but it is with equal propriety addressed to Christians, as the professed people of God. The foundation of the command is, that they professed to be his people, and that as his people they ought to be like their God. Compare Micah 4:5. It is a great truth, that people everywhere will imitate the God whom they worship. They will form their character in accordance with his. They will regard what he does as right. They will attempt to rise no higher in virtue than the God whom they adore, and they will practice freely what he is supposed to do or approve. Hence, by knowing what are the characteristics of the gods which are worshipped by any people, we may form a correct estimate of the character of the people themselves; and, hence, as the God who is the object of the Christian's worship is perfectly holy, the character of His worshipers should also be holy. And hence, also, we may see that the tendency of true religion is to make people pure. As the worship of the impure gods of the pagan moulds the character of the worshippers into their image, so the worship of Yahweh moulds the character of His professed friends into His image, and they become like him.

1:16 Lev 11:44.