The word holy is commonly understood to mean moral perfection. And when it is applied to God's relationship to "sinners" it suggests that God has such a high standard of holiness (moral perfection) that he will not tolerate or forgive sinners until they are sanctified and made holy (morally clean).
But this is not what the Hebrew prophets had in mind when they cried, "Holy! holy! holy is YHWH Sabaoth." The Hebrew kaddosh, has nothing to do with morality but means "otherness,"-- Wholly Other. "YHWH is other! other! other!"
YHWH does not conform to, or fit into our concepts of deity. He can not be defined by our abstract theistic characterizations (omnipotent, omniscient, impassible...). YHWH is radically, transcendentally different (other) then the gods made in our own image: the autocratic and domineering gods that are the projections of our primate animal nature.
God is radical, uncompromising, unconditional, self-emptying love for the other--us and all of creation. It is this love that defines His holiness. A love so completely open to the pain and need of the other; so inexhaustible in its selflessness; so broad and deep in its scope; that is could never be defined by any abstract philosophical/theological propositions. It could only be expressed and made real in a living person. Only in one who is the fulness of the humane and compassionate Abba. Only in the Crucified One: Jesus Christ.
The Molech Mentality