פּירוש אויף שמואל ב 6:7

“The Lord was angry at Uzzah, etc.” [6:7]. The Holy One killed Uzzah because he thought that the Ark would fall. He should have thought that the Ark was very holy and it would not fall, even if the oxen would fall. The Holy One said that the Ark carried the people who carried it. In any event, it would carry itself and would not fall. He punished Uzzah there, near the Ark.³Radak, II Samuel, 6:7.

Because of his mistake. Because of his mistake, he should have expounded a fortiori [as follows:] the Ark carried its own porters in the Yardein,⁷When Bnei Yisroel crossed the Yardein into the land of Yisroel as stated in Yehoshua 4:11 and explained in Sotah, ibid. isn't it all the more so [that it is able to carry] itself.