Sforno on Deuteronomy 33:19/ספורנו על דברים ל״ג:י״ט

1עמים הר יקראו, Issachar and Zevulun will call the nations of the earth to the “good mountain” with choice wares not to be found among those nations.

2שם יזבחו זבחי צדק, even the merchants of the gentile nations who had been offering sacrifices to “dead” deities all their lives, when they come to Jerusalem, the ”good mountain,” will offer sacrifices which qualify for the description “offerings of righteousness” (to the real G’d).

3כי שפע ימים יינקו, for Issachar and Zevulun draw from the riches of the sea among which are found such rare sources of colours as the chalazon worm from which techelet, blue wool is dyed. There one can also find a type of “white glass” or silicon on the beaches of the sea, much treasured for use in exotic goblets.