Charles Ellicott Commentary Isaiah 18:7

"In that time shall a present be brought unto Jehovah of hosts [from] a people tall and smooth, even from a people terrible from their beginning onward, a nation that meteth out and treadeth down, whose land the rivers divide, to the place of the name of Jehovah of hosts, the mount Zion." — Isaiah 18:7 (ASV)

In that time shall the present be brought ... —Not “of the people,” but a people, as they themselves are the present. The prophet foresees, as one result of the defeat of the Assyrian armies, that the nation, which he again describes instead of naming, will offer themselves to the service of Jehovah.

So understood, these words have an interesting parallel in Psalm 68:31, Ethiopia stretches out her hands unto God, or in the mention of Ethiopia in Psalm 87:3, as among the nations whose children are to be enrolled among the citizens of Zion. Messengers who may have confirmed Isaiah’s words were probably found among the envoys mentioned in 2 Chronicles 32:23. Here, again, the words have been referred, as before, to Israel.