and declare that this is what the Lord GOD says: Behold, I am against you, O Gog, chief prince of Meshech and Tubal.
God puts hooks in His enemy's jaws before the trouble even comes, so His people need not be frightened. He foresees those who will attack His church and declares Himself against them, yet turns even their wrath to His praise and the glory of His own name.
AI summary
Commenting on Ezekiel 38:1-13
And say, thus saith the Lord God, behold, I am against thee, O Gog, the chief prince of Meshech and Tubal. Which is repeated for the confirmation of it, that so it would certainly be; that the Lord, the mighty God, and King of kings, would in his providence frown upon him, and appear against him; and his titles are repeated also, to show that...
His high-sounding titles are repeated to imply the haughty self-confidence of the invader as if invincible.