וַיָּבֵ֤א אֶת־הַבַּדִּים֙ בַּטַּבָּעֹ֔ת עַ֖ל צַלְעֹ֣ת הָאָרֹ֑ן לָשֵׂ֖את אֶת־הָאָרֹֽן׃
And he put the staves into the rings on the sides of the ark, to bear the ark.
Read kabbalistic (mystical) interpretation of Exodus 37:5: and classical mystical sources.