The fault lay in the fact
that they never asked God how to transport the Ark. read chapter 15 verse 13.
Although we may be doing something "good" (here, bringing the Ark back to Jerusalem), that doesn't mean that we are doing what's "right." As 15:13 demonstrates, we must seek God for direction even before we do things that are "good." because like the proverb reads, there's a way that seems right to a man, but the end thereof is destruction. Uzzah clearly thought what he was doing was right. I'm sure any of us would have tried to "help" in the same way!
Created 11 months ago
