In 2nd Samuel we find a disturbing story of the death of Uzzah, by the hand of God. Here's the story: David had just been confirmed as king of all Israel, and he had established his home in Jerusalem. He wanted the Ark of the Covenant, which was the most important reminder of God's presence, to be in the city near him. The Ark had been in the home of Abinadab, a Levite who had a son named Uzzah.
David commanded the Ark be brought to Jerusalem, so Abinadab and Uzzah (and others) put the ornate chest on a cart pulled by two oxen. The oxen stumbled and Uzzah reached out and touched the Ark to prevent it from falling. That was a big no-no, and God killed him instantly.
Uzzah was, by human standards, a pretty good guy. He was serving God, doing the ministry that was prescribed him as a Levite. He was following the king's orders, and as far as we know, had no grievous sin like idolatry or sexual immorality.
So why did God kill Uzzah?
On the surface, Uzzah didn't follow the clear instructions God gave for doing his job. Sounds like following directions is pretty important to God, doesn't it? That is a pretty important lesson for children (and parents.)
At its deepest level, the story of Uzzah's sin points out our basic sin nature as humans. We want to do things our way, as we determine best. We don't want to follow God's way—God, who knows best, and deserves our fullest obedience. Isaiah 53:6 says this: "We all like sheep have gone astray. Each of us has gone his own way..."
That was Uzzah's chief sin. He knew, as a Levite (or should have known) that God had said specifically how His Ark was to be moved. Huzzah ignored God's directions regarding a holy thing: the Ark. God had promised to be present in the Ark, and He called it His Mercy Seat. That Ark was representative of how Israel was to approach God to receive mercy.
Even today, God prescribes how to approach Him to receive mercy—through Jesus Christ alone. But people want to use their own methods to get to God, or they ignore Him altogether. But there's no other way than the one Way; Jesus Himself. (John 14:6)
A person might be a 'good' guy, like Uzzah, with no 'major' sins to speak of. But the sin of Uzzah points to a holy God, with the sovereign right to determine how we approach Him. And truthfully, "there's none good but God," as Jesus said, and we all fall short of His glory. Uzzah speaks eloquently down through the ages: "Pay attention to the Way God provided for salvation. Don't try your own way."