Musar for Chullin 183:16

The staves by means of which the Ark was carried were not to be removed from the rings they sat in. These staves are symbolic of heads of households (non-scholars) who financially support those who study Torah. Our sages said אלמלא עליא, לא אתקיימו אתכליא, "without leaves the trunk could not continue to exist" (Chullin 92). Concerning this proverb the Torah says in Deut. 33,18: שמח זבולון בצאתך ויששכר באהלך, "Rejoice Zevulun when you depart (on your voyage to make a livelihood) and you Issachar within your tent." This means that those who support the ones who study Torah receive as much reward as those who study. This is the reason the staves were not to be removed from the Ark. Our sages went even further when they said that the reason Zevulun is mentioned first in the verse quoted, though he was the younger, is that it was he who enabled Issachar his brother to devote himself to Torah study on a full-time basis..