1 Kings 20:11

Overview - 1 Kings 20
Ben-hadad, not content with Ahab's homage, besieges Samaria.
13 By the direction of a prophet, the Syrians are slain.
22 As the prophet forewarned Ahab, the Syrians, trusting in the valleys, come against him in Aphek.
28 By the word of the prophet, and God's judgment, the Syrians are smitten again.
31 The Syrians submitting themselves, Ahab sends Ben-hadad away with a covenant.
35 The prophet, under the parable of a prisoner, making Ahab judge himself, denounces God's judgment against him.
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1 Kings 20:11  (King James Version)
And the king of Israel answered and said, Tell him, Let not him that girdeth on his harness boast himself as he that putteth it off.

Let not him, etc
This was no doubt a proverbial mode of expression. Jonathan renders it: "Let not him who girds himself, and goes down to battle, boast as one who has conquered and returned from it."
1 Samuel 14:6 1 Samuel 14:12 1 Samuel 14:13 ; 17:44-47 Proverbs 27:1 ; Ecclesiastes 9:11 ; Isaiah 10:15 Isaiah 10:16
Matthew 26:33-35 Matthew 26:75

The word harness is an obsolete word for armour, derived from the French {harnois;} see Exodus 13:18 .