Isaiah spoke eight times of God lifting up an ensign. From this we might gather what it means.
The first reference was against Jerusalem & Judah (Isaiah 5:26). They were God’s unproductive “vineyard”, of which he said he would remove the “hedge” & “fence” which seems equated to raise an ensign to the nations that they came swiftly, to carry them away to captivity.
The second reference (Isaiah 13:2) further explains this ensign as at that time Isaiah speaks in a prophecy about Babylon, and at that time the command goes out to lift up the ensign spoken of in chapter 5.
The third reference has two ensigns (Isaiah 11:10-12) , but they are the same. In the first instance the “root of Jesse” stands for the ensign, in the second the ensign is set up by God to gather the dispersed of Israel.
The fourth instance, shows the ensign to be put on the mountains as one the ambassadors of the nations should heed,
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 horn is blown, hear ye. For thus hath the LORD said unto me: I will hold Me still, and I will look on in My dwelling-place, like clear heat in sunshine, like a cloud of dew in the heat of harvest. (Isaiah 18:3-4)
This event seems to occur before God looks on his dwelling place. It makes sense that this ensign and blowing is at the return of Jesus.
The fifth instance a remnant of Judah is described as a lone beacon and ensign on a hill (Isaiah 30:17).
The sixth instance (Isaiah 31:9) is when Jews are asked to turn to the Holy One, in the day people cast away their idols (when the earth is shaken) and the princes of Assyria are dismayed by the ensign, which is associated with the fire of Zion and the furnace of Jerusalem.
The seventh instance the LORD God says he will lift up his hand to the nations and that is equated to being an ensign to the peoples (Isaiah 49:22). The hand is lifted up to bring the sons and daughters of Zion to him.
The last and 8th instance is most powerful as it indicates that we are to do something – not just watch.
I have set watchmen upon thy walls, O Jerusalem, they shall never hold their peace day nor night: ‘Ye that are the LORD’S remembrancers, take ye no rest, And give Him no rest, till He establish, and till He make Jerusalem a praise in the earth.’ The LORD hath sworn by His right hand, and by the arm of His strength: Surely I will no more give thy corn to be food for thine enemies; and strangers shall not drink thy wine, for which thou hast laboured; But they that have garnered it shall eat it, and praise the LORD, and they that have gathered it shall drink it in the courts of My sanctuary.
Go through, go through the gates, clear ye the way of the people; cast up, cast up the highway, gather out the stones; lift up an ensign over the peoples. Behold, the LORD hath proclaimed unto the end of the earth: say ye to the daughter of Zion: ‘Behold, thy salvation cometh; behold, His reward is with Him, and His recompense before Him.’ (Isaiah 62:6-11)
In this passage there are the watchmen who do not rest, but then presumably, when the time is right, people are to work hard clearing a highway, even to remove stones (perhaps of stumbling), and the ensign is to proclaim and prepare a way, speaking of the coming of the salvation. This is an ensign of another ensign to come.
For when the root of Jesse comes then he stands for the ensign which is the hand of God. And he gathers the natural daughters and sons of Zion to him from all the world.
An ensign in each instance speaks of gathering the people. But the idea of ensign in Hebrew also speaks of miracle.
Thou hast given a banner to them that fear thee, that it may be displayed because of the truth. Selah. (Psalm 60:4)