John Calvin Commentary Isaiah 18:1

"Ah, the land of the rustling of wings, which is beyond the rivers of Ethiopia;" — Isaiah 18:1 (ASV)

Woe to the land. I cannot determine with certainty what nation Isaiah speaks of, though he shows plainly that it bordered on Ethiopia. Some consider it to refer to the whole of Egypt, but this is a mistake, for in the next chapter he treats Egypt separately, from which it is evident that the people meant here were distinct from the Egyptians. Some think that the Troglodytes are meant here, which does not appear probable to me, for they had no intercourse with other nations because their language, as geographers tell us, was hissing and not speech; but those who are mentioned evidently had intercourse and leagues with other nations.

Still, it is uncertain whether they leagued against the Jews or joined with the Egyptians in driving out the Assyrians. If they were avowed enemies to the Jews, Isaiah threatens punishment; but if they deceived them by false promises, he shows that nothing is to be expected from them, because by idle messages they will only protract the time. However that may be, from the neighboring nations to be mentioned in the next chapter, we may in part ascertain where they were situated, that is, not far from Egypt and Ethiopia; yet some may be disposed to view it as a description of that part of Ethiopia which lay on the seacoast, for we shall afterwards see that the Assyrians were at war with the king of the Ethiopians (Isaiah 37:9).

When he says that that land shadows with wings, we learn from it that its sea was well supplied with harbours, so that it had many vessels sailing to it and was wealthy; for small and poor states could not maintain intercourse or traffic with foreign countries. He therefore means that they performed many voyages.