Quick answer
An offended brother fortifies: winning him back is harder than taking a walled city, because the quarrel has built castle bars across a door that once stood open.
Read both lines
The military comparison hands the advantage to the wound: armies have taken strong cities; the estranged brother has repelled longer sieges. And bars are deliberate architecture: the offended heart does not drift away, it builds, each replayed grievance another beam across the gate, until the person who once had free entry stands outside walls purpose-built against them. The warning: handle the near relationships gently, because their ruins fortify like nothing else. The mercy: if you stand outside such a wall, know what you are approaching. Fortresses are not taken by one apology fired over the wall; they open slowly, from the inside, usually to patience, humility, and time.
Related: Proverbs 17:14 · Matthew 5:23–24 · Ephesians 4:26–27
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
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