The Levites took up the ark - i. e., such of the Levites as were also priests (compare 2 Chronicles 5:7; 1 Kings 8:3).
Matthew Henry
Concise Bible Commentary
The ark was a type of Christ, and, as such, a token of the presence of God. That gracious promise, Lo, I am with you alway, even unto the end of the world, does, in effect, bring the ark into our religious assemblies, if we by faith and prayer plead that promise; and this we should be most earnest for. When Christ is formed in a soul, the law written in the heart, the ark of the covenant settled there, so that it becomes the temple of the Holy Ghost, there is true satisfaction in that soul.
SDA Bible Commentary (limited)
Volume 1-7
4. The Levites. The parallel passage reads, “the priests” (1 Kings 8:3). The record further states that “the priests brought in the ark” (2 Chron. 5:7). So “Levites” here must mean such Levites as were sons of Aaron and hence priests.