What does Psalm 48:5 mean?
Those who attacked Jerusalem (Psalm 48:4), thinking they could conquer it, instead fled in terror. This continues a description of the holy city as an example of God's power and might (Psalm 48:1–3).An event commonly associated with this passage is the failed siege of Jerusalem by the Assyrian forces of Sennacherib (2 Kings 19). The victory began when Hezekiah, King of Judah, entered the temple (Isaiah 37:1). In distress, he sent a message to the prophet Isaiah requesting prayers (Isaiah 37:1–4). Isaiah responded by telling Hezekiah not to be afraid, because the Lord would deal with the Assyrians (Isaiah 37:5–7). Hezekiah later prayed over a threatening note he received from the Assyrians (Isaiah 37:14–20). The Lord answered Hezekiah's prayer (2 Kings 19:35–37).
Another option is the defeat of a coalition which assembled to attack Jerusalem during the reign of Jehoshaphat. That combined force turned to infighting and self-destructed without Israel needing to fight, at all (2 Chronicles 20).
