פירוש על דברים 33:18

ולזבולן אמר AND OF ZEBULUN HE SAID — These five tribes whom he blessed last, Zebulun, Gad, Dan, Naphtali and Asher, it repeats their names in order to instil them with strength and power, because they were the weakest of all the tribes. They are the very same whom Joseph took to Pharaoh, as it is said, (Genesis 47:2, cf. Rashi thereon) “And of the least of his brothers he took five men [and placed them before Pharaoh]” — because these looked weak, so that he (Pharaoh) should not appoint them his war officers (Bava Kamma 92a).

REJOICE, ZEBULUN, IN THY GOING OUT — that is, when you journey in merchant-ships. He alludes to [what Jacob said of Zebulun that] he shall dwell at the shore of the sea.²³⁷Genesis 49:13. And you Issachar [rejoice] in thy tents, thus intimating that Issachar saw a resting-place that it was good, and his land that it was pleasant,²³⁸Ibid., Verse 15. in accord with Jacob’s blessing.

שמח זבלון בצאתך, "Rejoice, O Zevulun, on your journeys;" Although as a general rule we are not supposed to rejoice as per Kohelet 2,2 ולשמחה םה זה עושה, "and of joy, what does it accomplish?" Moses says here that Zevulun goes to sea joyfully even though he leaves the halls of Torah study in order to engage in commerce. The reason he is entitled to do this is that the proceeds of his commerce are intended to enable Issachar to devote himself to uninterrupted Torah study.