| Barnes' Notes on the Bible The "due order" was that the ark should be borne on the shoulders of Kohathite Levites - not that it should be placed upon a cart, drawn by oxen, and rudely shaken.
Gill's Exposition of the Entire BibleFor because ye did it not at the first,.... Did not sanctify themselves, as the supplement in our version directs; but rather the sense is, ye were not there at first, when the ark was brought from Kirjathjearim as far as the house of Obededom, as they should have been; they were not then employed, as was their business, and therefore the Lord our God made a breach upon us; by smiting Uzzah with death, who was no Levite, and touched the ark, which is called his "error", and for which God smote him, 2 Samuel 6:7 on which place Lud. Capellus observes, the word "shal", we there render "error", signifies a "disease" in the Arabic language, and might formerly design a sudden one with the Hebrew; as an apoplexy; and so the sense be, that God smote Uzzah with an apoplexy, of which he suddenly died: for that we sought him not after the due order; but, instead of employing the Levites to carry the ark on their shoulders, it was put upon a cart.
Keil and Delitzsch Biblical Commentary on the Old Testament"For because in the beginning (i.e., when the ark was removed from the house of Amminadab, 1 Chronicles 13:1-14) it was not you (sc., who brought it up), did Jahve our God made a breach upon us," sc. by the slaying of Uzza, 1 Chronicles 13:11. In the first clause the predicate is wanting, but it may easily be supplied from the context. The contracted form למבּרשׁונה, made up of למה and בּראשׁונה, is unique, since מה is so united only with small words, as in מזּה, Exodus 4:2, מלּכם, Isaiah 3:15; but we find מתּלאה for מה־תּלאה, Malachi 1:13; cf. Ew. 91, d. למה here signifies: on account of this which equals because; cf.'Ew. 222, a, and 353, a. "This was done, because we did not seek Him according to the right," which required that the ark, upon which Jehovah sits enthroned, should be carried by Levites, and touched by no unholy person, or one who is not a priest (Numbers 4:15).
Geneva Study BibleFor because ye did it not at the first, the LORD our God made a breach upon us, for that we sought him not after the due {f} order. (f) According as he has appointed in the law.
Matthew Henry's Concise Commentary15:1-24 Wise and good men may be guilty of oversights, which they will correct, as soon as they are aware of them. David does not try to justify what had been done amiss, nor to lay the blame on others; but he owns himself guilty, with others, of not seeking God in due order | 
