‘ And the anger of YHWH was kindled against Uzzah, and God smote him there for his error, and there he died by the ark of God.'
God knew what was in Uzzah's heart, even if we do not. And what happened next would have surprised no one who saw what he had done. Indeed they would have expected it. Had it not happened it could have caused great harm and confusion to them in their inner thinking. It would have decreased the significance of the Ark. (We must remember that this was in a day when to approach a king incorrectly could lead to the death penalty, and when to touch the king's person could be seen as treason). There are some things the effects of which are considered to be so enormous that they must be prevented at all costs, and this was one of them. In fact we can truly say that for God not to have acted would probably have debased the whole religion of Israel in the eyes of Israel and have reduced it to idolatry. For the Ark bore the Name, and thus bore the One Who invisibly sat on it between the cherubim (the writer reminded us of that quite deliberately in 2 Samuel 6:2). So for there to be no reaction to its being touched would have debased the idea of the true fear of God and the reality of His invisible presence. It would have been a barrier in the future to man's true appreciation of the ‘otherness' and holiness of God, and yet of His closeness to His people. (Spiritual conceptions in those days were very tied up with physical things). It would have contradicted the idea that in some unique way God was present where His Ark was. Idolatrous images could be touched precisely because of the nature of their gods. So by his action Uzzah was simply demoting God to having the same nature as an idol.
God knew all that and acted. His wholehearted antipathy to what Uzzah had done was revealed by His smiting him in such a way that he died. It was an indication that God was ‘angry' (reacting against Uzzah) because He knew Uzzah's thoughts and the effect that Uzzah's action could have had on men's thinking and approach to Him, and no doubt also because He knew what it revealed about Uzzah's own innermost attitude of heart. He had committed a ‘sin unto death'.
YHWH's action here may appear extreme to us but it settled in men's hearts from this moment on the recognition that He was not in any way of this world, that no priest or other personage, not even the ‘keeper of the Ark', could fully act in His Name, or usurp His rights, or claim special privilege in dealings with Him. All must for ever be obedient, and subservient to His will, and act as He revealed, and not the other way round, and it emphasised that He stood alone because He was ‘wholly other'. The dead body lying sprawled on the cart thus became a permanent warning for the future that God was such that He was not to be trifled with, and of what happened to any who ignored His strict requirements. As a result the holiness of the Ark was enhanced, and its continuing significance emphasised. Indeed had Israel learned the lesson that was taught here the new kingdom would have progressed and grown and all that followed would never have happened. That was how important the lesson was. They were to recognise that the Holy One of Israel was truly among them. (The failure to learn that lesson did not just result in one man being struck down, it finally resulted in many being struck down and Jerusalem and the Temple being totally destroyed).
What happened to Uzzah here can be compared with what happened to Nadab and Abihu when the initial covenant had been established under Moses, something which had also commenced a new beginning for God's people (Leviticus 10:1-2); with what had happened to Achan at the new entry into the land when God's kingly rule was initially being established in Canaan (Joshua 7), and with what would one day happen to Ananias and Saphira at the commencement of an even greater Kingly Rule (Acts 5:1-11). In all these cases they were people who failed to obey God implicitly at the commencement of a new phase in His kingly rule, and treated lightly their response towards Him, and discovered the consequences.