Verse 18. "I have made thee this day a defenced city, and an iron pillar, and, brazen walls" - Though thou shalt be exposed to persecutions and various indignities, they shall not prevail against thee. To their attacks thou shalt be as an impregnable city; as unshaken as an iron pillar; and as imperishable as a wall of brass. None, therefore, can have less cause to apprehend danger than thou hast. The issue proved the truth of this promise: he outlived all their insults; and saw Jerusalem destroyed, and his enemies, and the enemies of his Lord, carried into captivity. Instead of twmj chomoth, walls, many MSS. and editions read tmj chomath, a wall, which corresponds with the singular nouns preceding.
Verse 19. "They shall not prevail against thee" - Because I am determined to defend and support thee against all thy enemies. One of the ancients has said, qeou qelontov, kai epi ripov pleh swzh Thestius, apud Theophil. ad Autolyc. lib. ii. " God protecting thee, though thou wert at sea upon a twig, thou shouldst be safe."