Isaiah 18:3

1 Woe to the land of whirring wings, along the rivers of Cush,

2 which sends couriers by sea, in papyrus vessels on the waters. Go, swift messengers, to a people tall and smooth-skinned, to a people widely feared, to a powerful nation of strange speech, whose land is divided by rivers.

All you people of the world and dwellers of the earth, when a banner is raised on the mountains, you will see it; when a ram’s horn sounds, you will hear it.

4 For this is what the LORD has told me: “I will quietly look on from My dwelling place, like shimmering heat in the sunshine, like a cloud of dew in the heat of harvest.”

5 For before the harvest, when the blossom is gone and the flower becomes a ripening grape, He will cut off the shoots with a pruning knife and remove and discard the branches.

This was said to Israel at a particular time, so it is wise to read it together with the surrounding text. Do read the surrounding verses too, because the context often says more than a single verse.

Compare

BSB
All you people of the world and dwellers of the earth, when a banner is raised on the mountains, you will see it; when a ram’s horn sounds, you will hear it.
KJV
All ye inhabitants of the world, and dwellers on the earth, see ye, when he lifteth up an ensign on the mountains; and when he bloweth a trumpet, hear ye.
WEB
All you inhabitants of the world, and you dwellers on the earth, when a banner is lifted up on the mountains, look! When the trumpet is blown, listen!
ASV
All ye inhabitants of the world, and ye dwellers on the earth, when an ensign is lifted up on the mountains, see ye; and when the trumpet is blown, hear ye.
DARBY
All ye inhabitants of the world, and dwellers on the earth, when a banner is lifted up on the mountains, see ye, and when a trumpet is blown, hear ye!
BLB
All [you] dwellers of the world and dwellers of the earth—at the lifting of a banner [in] the mountains, you⁺ will see [it], and at the blowing of a shofar, you⁺ will hear [it].
ÅB
Alle dere jorderikes innbyggere, dere som bor på jorden! Når det løftes banner på fjellene, da se til, og når det støtes i basun, da hør etter!
OTB
Alle dere innbyggere i verden, dere som bor på jorden, når et banner heves på fjellene, vil dere se det, og når trompeten lyder, vil dere høre det.
B1930
Alle I jorderikes innbyggere, I som bor på jorden! Når det løftes banner på fjellene, da se til, og når det støtes i basun, da hør efter!

Study notes (Tyndale)

Original text and word study

Cross references