What is this holiness?

[W]hile the motif of holiness may be found widely in ANE religions in religious-cultic settings, it appears with distinctive wrinkles in the HB (see Exod 34:11–17; 2 Kgs 21:4–9), where God is the source of holiness (“the holy one of Israel”; 2 Kgs 19:22) and calls Israel to be holy (Lev 11:44). God’s holiness is concentrated in the temple in Jerusalem and its sacrificial system (see Lev 1–7) but also extends throughout the land of Israel, and so it is important that God’s commandments be observed throughout the land (Lev 18:1–5, 24–30): the people were not only to eschew idolatry but also to honor parents, observe religious festivals that bound the community together, provide for the poor, and so on (Lev 19:3–37).—M. Patrick Graham in Divine Doppelgängers: YHWH’s Ancient Look-Alikes, pp. 135–36