John Gill Commentary Zechariah 2:9

"For, behold, I will shake my hand over them, and they shall be a spoil to those that served them; and ye shall know that Jehovah of hosts hath sent me." — Zechariah 2:9 (ASV)

For, behold, I will shake mine hand upon them The nations; either the Babylonian, or the antichristian states; meaning, that he would exert his power, and inflict punishment on them, and utterly destroy them; which would be done by the bare shaking of his hand.

and they shall be a spoil to their servants As the Babylonians were to the Persians; not through Cyrus, which had been done; but through Darius, who took Babylon, after a siege of twenty months, and put great numbers to death; and all became a spoil to the Persians, who had been their servants: or the ten kings, that gave their kingdoms to the beast, and were subject to him; but now shall hate the whore, and eat her flesh; and all her riches and revenues shall be a spoil unto them, and be divided among them, (Revelation 17:12Revelation 17:16).

and you shall know that the Lord of hosts has sent me Either the Prophet Zechariah, that he was a true prophet, and had his mission from the Lord of hosts, as will appear by the accomplishment of these prophecies; or rather Christ, sent by God the Father; and who will be known and owned by the Jews, as well as by the Gentiles, to be the sent of God, when they shall be converted, and antichrist shall be destroyed. Kimchi refers this, and the following verse (Zechariah 2:10) , to the times of the Messiah.