The passage in 2 Sam. 6 you have in mind, about the death of Uzzah (who is not be confused with Uzziah BTW, who was a king of Judah) treats holiness as a power which can kill those who do not come to holy things in the proper way. This kind of holiness is not moral in character - this is holiness thought of as being like electricity: as being a force, and not much else.
Holiness is not always thought of as implying ethical goodness - gods could do all sorts of things which we, being Christians, consider immoral; not because they were immoral,
but because they were divine beings; they were “not-human”; and this “not-humanness”, this status of being wholly
different *from *man, is what holiness amounted to in the world in which much of the OT was written. The basic thing about being a god or being holy is, that one is
set apart from all other things; one has nothing in common with them; what was not holy, was “profane” (pro fanum = “outside the temple” = not holy). So when a holy thing - like the Ark of the Covenant - came into contact with unholy people, trouble was the result. Sin was anything that disturbed the relationship of gods to men - a lie could so, but so could a flaw in the ritual of worship.
The way to avoid being struck down by the holiness of holy things, was to come properly prepared (if one was a priest) or to get the appropriate person to come between oneself and the dangerousness of the holiness of the holy thing or being; that’s what priests were for - they had immediate access to the holy gods, on behalf of the “profane”, “unclean” “not-holy” people; as long as they were properly prepared; otherwise even priests could be destroyed; like Nadab & Abihu, the sons of Aaron.
This is not Christian holiness,
which is holiness as likeness to God. Christian holiness includes ethical likeness to God, & it goes beyond ethics. This is holiness as goodness. God remains “Wholly Other”,
wholly different from created beings - but in Christ He has taken our nature to Himself, so that we can approach Him without being destroyed. The Israelites needed Moses to get between God & them, so that Moses could absorb the force of God’s Holiness. As Our Mediator, Jesus took the full force of the Righteous Wrath of God upon our sins - that is why we don’t need any Sacrifice but His.
As He was a man in every sense - apart from His sinlessness - He acted as one, and could be encountered as one. Only on exceptional occasions in His earthly life was there a hint that He was more than man; such as the Transfiguration.
It’s also important for us to appreciate that the revelation witnessed to in the Bible is gradual - that is one reason the notion of holiness taken for granted in 2 Sam. 6 is not the same in kind as the holiness of Jesus; there has been education by God of His People in the meantime. ##