John Calvin Commentary Psalms 72:8

"He shall have dominion also from sea to sea, And from the River unto the ends of the earth." — Psalms 72:8 (ASV)

He shall have dominion from sea to sea. As the Lord, when He promised His people the land of Canaan for an inheritance, assigned to it these four boundaries (Genesis 15:18), David indicates that as long as the kingdom continues to exist, the possession of the promised land will be complete, to teach the faithful that the blessing of God cannot be fully realized, except while this kingdom flourishes.

He therefore declares that He will exercise dominion from the Red Sea, or from that arm of the Egyptian sea to the sea of Syria, which is called the Sea of the Philistines, and also from the river Euphrates to the great wilderness. If it is objected that such narrow boundaries do not correspond with the kingdom of Christ, which was to be extended from the rising of the sun to its setting, we reply that David obviously adapts his language to his own time, as the full extent of the kingdom of Christ had not yet been fully unfolded.

He has therefore begun his description in language well known and in familiar use under the Law and the Prophets; and even Christ Himself began His reign within the limits here marked out before He reached the uttermost boundaries of the earth, as it is said in Psalm 110:2:

The Lord shall send the rod of thy strength out of Zion.

But soon after, the Psalmist proceeds to speak of the expanded extent of the empire of this king, declaring that the kings beyond the sea will also be tributaries to him, and that the inhabitants of the desert will receive his yoke.

The word ציים, tsiim, which we have translated inhabitants of the desert, is, I have no doubt, to be understood as referring to those who, dwelling towards the south, were at a great distance from the land of Canaan. The Prophet immediately adds that the enemies of the king shall lick the dust as a sign of their reverence.

This ceremony, as is well known, was customary in ancient times among the nations of the East. Alexander the Great, after he had conquered the East, wished to compel his subjects to practice it, which led to great dissatisfaction and conflict, as the Macedonians disdainfully refused to yield such a slavish and degrading mark of subjection.

The meaning, then, is that the king chosen by God in Judea will obtain so complete a victory over all his enemies, far and wide, that they will come humbly to pay him homage.