1 Chronicles 15:15

And the children of the Levites bare the ark of God upon their shoulders, with the staves thereon, as Moses commanded, according to the word of the Lord. Not only bare it on their shoulders, but with the staves in it, which rested on their shoulders, see Numbers 7:9, the reason of this command, that the ark should be carried on men's shoulders, and not in any carriage, according to Maimonides (h), was both for the honour of it, and lest its form and structure should be any ways damaged.

(h) Moreh Nevochim, par. 3. c. 45. p. 479.