I have given him the land of Egypt as the reward for his labor, because it was done for Me, declares the Lord GOD.
God gives Egypt to him as wages because he and his army worked for Him.
This verse interprets Babylon's campaign as unwitting service to God.
17In the twenty-seventh year, on the first day of the first month, the word of the LORD came to me, saying, 18“Son of man, Nebuchadnezzar king of Babylon caused his army to labor strenuously against Tyre. Every head was made bald and every shoulder made raw. But he and his army received no wages from Tyre for the labor they expended on it. 19Therefore this is what the Lord GOD says: I will give the land of Egypt to Nebuchadnezzar king of Babylon, who will carry off its wealth, seize its spoil, and remove its plunder. This will be the wages for his army. 20I have given him the land of Egypt as the reward for his labor, because it was done for Me, declares the Lord GOD. 21In that day I will cause a horn to sprout for the house of Israel, and I will open your mouth to speak among them. Then they will know that I am the LORD.”