וַיִּשָּׂאֻ֗הוּ מִבֵּ֤ית אֲבִֽינָדָב֙ אֲשֶׁ֣ר בַּגִּבְעָ֔ה עִ֖ם אֲר֣וֹן הָאֱלֹהִ֑ים וְאַחְי֕וֹ הֹלֵ֖ךְ לִפְנֵ֥י הָאָרֽוֹן׃
И вывели его из дома Авинадаба, который был на холме, с ковчегом Божиим, и Ахио пошел перед ковчегом.
Rashi
drove the cart as is the custom of cart drivers, one walks in front of the cart and directs it in a straight way, and one is alongside the cart, so that it does not turn over and fall. And so it is written (II Sam. 6: 4): “... and Ahio went before the Ark,” and Uzza was alongside the cart; therefore, Uzza stretched forth his hand to take hold of the Ark when the oxen swayed it, and therefore, he was punished.