Deuteronomy 33:19

The people] RV 'peoples,' their heathen neighbours who trade with them, particularly the Phoenicians. These they are here said to call unto the mountain where they offer sacrifices of righteousness, i.e. sacrifices that are offered rightly. It would appear that in the land of Zebulun and Issachar there were certain mountain sanctuaries where sacrificial feasts were held to which these tribes were wont to invite their neighbours, and that these gatherings were a source of commercial advantage to them. The abundance of the seas refers to the maritime commerce mentioned above, and the treasures hid in the sand have been supposed to refer to the manufacture of glass for which the sands at the mouth of the river Belus, which flows into the Bay of Acre, were famous. The Roman historian Pliny says indeed that it was here that glass was first invented or discovered by some sailors who lit a fire upon the sand and accidentally produced glass.