6:3 And they set the ark of God upon a new cart, and brought it out of the house of Abinadab that was in Gibeah: and Uzzah and Ahio, the sons of Abinadab, drave the new cart.
The story of David's new cart and its results is a striking illustration of the spiritual truth that blessing does not follow even the best intentions in the service of God except as that service is rendered in God's way. It is a constant point of failure. God had given explicit directions how the ark should be borne. Numbers 4:1-15 but David adopted a Philistine expedient.