Or HaChaim on Exodus 35:12/אור החיים על שמות ל״ה:י״ב

1 את הארון ואת בדיו, The Holy Ark and its staves, etc. The Torah lists the most sacred of the furnishings of the Tabernacle first just as it started by mentioning the most sacred of the various covers of the Tabernacle, the ones made of twisted linen first in 36,8. The reason that the staves are mentioned next with the conjunctive letter ו is that they formed an integral part of the Holy Ark and were not allowed to become detached from it as we have been told in 25,16. The Torah next mentions the lid of the Holy Ark, omitting the conjunctive letter ו, seeing that it was not as sacred as the Holy Ark itself. The fact that it was not attached permanently to the Holy Ark also suggests that it was not as sacred as the Ark itself. On the other hand, the dividing curtain, פרוכת המסך is introduced by the Torah with the conjunctive letter ו, indicating that it was of the same level of sanctity as the lid on the Ark.