Charles Ellicott Commentary 2 Samuel 6:13

"And it was so, that, when they that bare the ark of Jehovah had gone six paces, he sacrificed an ox and a fatling." — 2 Samuel 6:13 (ASV)

Those who bore the ark. —David no longer presumed to violate the law, but took care that the ark should be borne by the proper persons. In 1 Chronicles 15, a detailed account is given of the sanctification of the priests and Levites for this purpose, and of the musical arrangements.

Had gone six paces. —As soon as the removal of the ark had been successfully begun, David offered sacrifices of thanksgiving and prayer. Again, when the journey was completed, they offered burnt sacrifices and peace offerings before God (2 Samuel 6:17; 1 Chronicles 16:1). The work was begun and ended with solemn sacrifice. It is quite unnecessary to suppose that offerings were made at each six steps of the way, for although this might have been possible, it is not recorded. Of course, David offered these sacrifices, like all Israel (1 Kings 8:62), through the ministration of the priests whom he had called together.