Thomas Aquinas

Verse 9 thus refers: "Her gates have sunk into the ground", That is, the ground filled with tribulations, and so unable to be torn up. Psalm 69:2 thus states: "I sink in deep mire, where there is no foothold." Again: "her gates", That is, the kings for whom there is the power of a judge who is exercised at the gates, (of the city, Jerusalem). Also: "he has ruined and broken her bars." That is by capturing and leading her into captivity. So: "her bars", namely princes in whom the kingdom is entrusted regarding its gates and bars. …

Commentary on Lamentations ↗