But when they came to the threshing floor of Nacon, Uzzah reached out toward the ark of God and took hold of it, for the oxen nearly upset it. And the anger of the LORD burned against Uzzah, and God struck him down there for his irreverence; and he died there by the ark of God.

“Then the anger of the LORD was aroused against Uzza, and He struck him because he put his hand to the ark; and he died there before God” (1 Chronicles 13:10). It seemed to have been an automatic reaction on the part of Uzzah, but God regarded his actions as so serious that He struck him down dead.

And the anger of the Lord was kindled against Uzzah. And God struck him there for the error (2Samuel 6:3, 6 - 7, HBFV throughout). Uzzah was killed by God for impulsively touching the ark in an attempt to prevent it from possibly falling out of its cart.

When the oxen stumbled, making the ark tilt, Uzzah steadied the ark with his hand, in direct violation of the divine law, and he was immediately killed by the Lord for his error.