God’s holiness refers to two distinct but related ideas. First the term holy calls attention to God’s “otherness,” the sense in which he is different from and higher than we are. It calls attention to his greatness and his transcendent glory. The second meaning of holiness has to do with God’s purity. The perfection of his righteousness is displayed in his holiness.
Sproul, R.C.; Grace Unknown: The Heart of Reformed Theology; Baker Books; Grand Rapids, MI; copyright 1997; p. 38-39