Make bright the arrows; gather the shields: the LORD hath raised up the spirit of the kings of the Medes: for his device is against Babylon, to destroy it; because it is the vengeance of the LORD, the vengeance of his temple.
Make bright - literally, pure. Polish and sharpen "the arrows."
Gather - literally, fill; i:e., gather in full number "the shields," so that none be missing. So, "gave in full tale" (1 Samuel 18:27). Gesenius, not so well, translates, 'Fill with your bodies the shields' (cf. Song of Solomon 4:4). He means to tell the Babylonians, Make what preparations you will, all will be in vain (cf. Jeremiah 46:3-6).
The Lord hath raised up the spirit of the kings of the Medes. He names the Medes rather than the Persians, because Darius, or Cyaxares, was above Cyrus in power and the greatness of his kingdom.
It is the vengeance of the Lord, the vengeance of His temple - (Jeremiah 50:28).