1 Chronicles 15:14

So the priests and the Levites sanctified themselves to bring up the ark of the LORD God of Israel.

The priests and the Levites sanctified or consecrated themselves to bring up the ark of the Lord God of Israel to Jerusalem, showing that those entrusted with this sacred duty prepared themselves as God required. This consecration belonged to the proper return and placement of the ark at Jerusalem after it had been removed from the tabernacle at Shiloh and afterward brought from the house of Obed-edom, and its arrival was a joyful event. The verse stands in 1 Chronicles 4-19, a portion largely of chronology and long, tedious records of names that yet contains beautiful gems illuminating the record, showing the preservation of the records of God's children and the integrity of the tribes, especially the careful preservation of the genealogy of the tribe of Judah through whom Christ came.

The sanctification corrected an earlier failure in which the ark was carried on a cart in the manner of the Philistines rather than in the appointed way, when Uzza was struck. David recognized that the judgment came from failure to follow the due order and directed the priests and Levites to prepare themselves and carry the ark as ordained. The ordained manner was to bear the ark on the shoulders in its appointed order according to God's instructions given through Moses, rather than placing it on a cart or touching it.

The appointed shoulder-bearers were specifically the Kohathite Levites. They were the Levites serving in their proper order, carrying the ark on their shoulders in the proper order rather than transporting it on a cart. The ark was to be moved on the shoulders of the priests rather than on a cart, according to God's appointed order. A prophet's instructions remain binding after the prophet's death, and human judgment is unsafe when it sets those instructions aside. Acceptable service to God follows His word rather than heathen customs, and God's sacred institutions are not to be replaced with humanly chosen substitutes.