Albert Barnes Commentary Psalms 102:15

"So the nations shall fear the name of Jehovah, And all the kings of the earth thy glory." — Psalms 102:15 (ASV)

So the heathen - The nations. That is, the surrounding people, who hear what you have done for your people, will see the evidence that you are God and learn to love and worship you.

Shall fear the name of the Lord - Shall reverence and honor you.

And all the kings of the earth thy glory - The sovereigns of the earth will be especially affected and impressed with your majesty. If this refers to the return from the captivity at Babylon, then it means that event would be particularly suited to impress the minds of the rulers of the world, as showing that God had all nations under His control, that He could deliver a captive people from the grasp of the mighty, that He was the friend of those who worshipped Him, and that He would frown on oppression and wrong.