You shall be holy, for I the LORD your God am holy…You shall not hate in your heart anyone of your kin…you shall not take vengeance or bear a grudge against any of your people, but you shall love your neighbour as yourself: I am holy. Lev 19:2, 17,18
Often we equate holiness with morality. But isn’t it first a call to relationship with God? Holy is the way God is, and we are invited to join God in God’s way of being. Holiness is about a relationship with God, and this relationship has consequences. Read Leviticus 19 with this as a priority in your interpretation rather than through a moral lens and see what happens. I find that the passage changes from a set of demands that I must fulfil to a call to union with God.
It is often noted that the meaning of holiness is separation. God is holy, not like the gods of the nations, and the people of God are to be separate from the nations around. (Lev 20:26) However, this isn’t a call to become a cult. Jesus hung with tax collectors and sinners; presumably, he was holy at the time. Indeed, this is crucial. In the Hebrew Scriptures, it is God’s presence (a presence enacted in liberation and covenant) that makes the people holy. (Lev 22:32-33) God’s presence in covenant and liberation finds its apogee in Jesus. In Christ God comes to us as one of us (this gives us a clue about the deepest practice of holiness) to make us holy. (Rom 1:2 cf. 1:30)