Revelation 9:12-14

 "And behold, I am coming quickly. 

Blessed is he who heeds the words of the prophecy of this book."     

Revelation 22:7  NASB

The first woe is past; two other woes are yet to come. The sixth angel sounded his trumpet, and I heard a voice coming from the four horns of the golden altar that is before God. It said to the sixth angel who had the trumpet, "Release the four angels who are bound at the great river Euphrates."

The first woe is past; two other woes are yet to come 
Revelation 8:13  As I watched, I heard an eagle that was flying in midair call out in a loud voice: "Woe! Woe! Woe to the inhabitants of the earth, because of the trumpet blasts about to be sounded by the other three angels!" 

I heard a voice coming from the four horns 
Exodus 30:1-3  "Make an altar of acacia wood for burning incense. It is to be square, a cubit (about 18 inches) long and a cubit wide, and two cubits high--its horns of one piece with it. Overlay the top and all the sides and the horns with pure gold, and make a gold molding around it."

of the golden altar that is before God 
Revelation 8:3  Another angel, who had a golden censer, came and stood at the altar. He was given much incense to offer, with the prayers of all God's people, on the golden altar in front of the throne.

Release the four angels 
Revelation 7:1  After this I saw four angels standing at the four corners of the earth, holding back the four winds of the earth to prevent any wind from blowing on the land or on the sea or on any tree. 

who are bound at the great river Euphrates 
Genesis 15:18  On that day the LORD made a covenant with Abram and said, "To your descendants I give this land, from the Wadi of Egypt to the great river, the Euphrates--..."
Deuteronomy 1:7-8  "Break camp and advance into the hill country of the Amorites; go to all the neighboring peoples in the Arabah, in the mountains, in the western foothills, in the Negev and along the coast, to the land of the Canaanites and to Lebanon, as far as the great river, the Euphrates. See, I have given you this land. Go in and take possession of the land the LORD swore he would give to your fathers--to Abraham, Isaac and Jacob--and to their descendants after them."
Joshua 1:4  "Your territory will extend from the desert to Lebanon, and from the great river, the Euphrates--all the Hittite country--to the Mediterranean Sea in the west."
Isaiah 11:15  The LORD will dry up the gulf of the Egyptian sea; with a scorching wind he will sweep his hand over the Euphrates River. He will break it into seven streams so that anyone can cross over in sandals.
Revelation 16:12  The sixth angel poured out his bowl on the great river Euphrates, and its water was dried up to prepare the way for the kings from the East.

(parentheses are mine)

Scriptures taken from the Holy Bible, New International Version® NIV®, Copyright© 1973, 1978, 1984, 2011 by Biblica, Inc.® Used by permission. All rights reserved worldwide. 
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