John Gill Commentary 1 Chronicles 15:14

"So the priests and the Levites sanctified themselves to bring up the ark of Jehovah, the God of Israel." — 1 Chronicles 15:14 (ASV)

So the priests and the Levites sanctified themselves
As they were ordered, and in the manner they should:

to bring up the ark of the Lord God of Israel ;
for though it was chiefly the work of the Levites, yet the priests might do it, and sometimes did, see (Joshua 3:13Joshua 3:14) (6:6) .