God is speaking of Israel to Ethiopia here
Isa 18:1 Listen, Ethiopia [fn]—land of fluttering sails [fn]
that lies at the headwaters of the Nile,
Isa 18:2 that sends ambassadors
in swift boats down the river.
Go, swift messengers!
Take a message to a tall, smooth-skinned people,
who are feared far and wide
for their conquests and destruction,
and whose land is divided by rivers.
Isa 18:3 All you people of the world,
everyone who lives on the earth—
when I raise my battle flag on the mountain, look!
When I blow the ram's horn, listen!
Isa 18:4 For the LORD has told me this:
"I will watch quietly from my dwelling place—
as quietly as the heat rises on a summer day,
or as the morning dew forms during the harvest."
Isa 18:5 Even before you begin your attack,
while your plans are ripening like grapes,
the LORD will cut off your new growth with pruning shears.
He will snip off and discard your spreading branches.
Isa 18:6 Your mighty army will be left dead in the fields
for the mountain vultures and wild animals.
The vultures will tear at the corpses all summer.
The wild animals will gnaw at the bones all winter.
Isa 18:7 At that time the LORD of Heaven's Armies will receive gifts
from this land divided by rivers,
from this tall, smooth-skinned people,
who are feared far and wide for their conquests and destruction.
They will bring the gifts to Jerusalem, [fn]
where the LORD of Heaven's Armies dwells.
The wise men brought gifts to Jesus upon his birth. Israel is where God dwelt.