And Tyre did build herself a stronghold - She built it for herself, not for God, and trusted to it, not to God, and so its strength brought her the greater fall. The words in Hebrew express yet more. "Tyre" (Zor) literally, "the rock," "built herself mazor, tower," a rock-like fort, as it were, a rock upon exceeding strength, binding her together. . "The walls, 150 feet high and of breadth proportionate, compacted of large stones, embedded in gypsum," seemed to defy an enemy who could only approach her by sea. "In order to make the wall twice as strong they built a second wall ten cubits broad, leaving a space between of five cubits, which they filled with stones and earth." Yet high walls do not fence in only; they also hem in. Mazor is both "a stronghold" and "a siege." Wealth and strength, without God, do but invite and embitter the spoiler and the conqueror."
And she heaped up silver as the dust, and fine gold as the mire of the streets - "Though he heap up silver as the dust," Job says, "The King" Job 27:16, Solomon, "made silver in Jerusalem as stones" 2-Chronicles 9:27. Through her manifold commerce she gathered to herself wealth, as abundant as the mire and the dust, and as valueless. "Gold and silver," said a pagan, "are but red and white earth." Its strength was its destruction. Tyre determined to resist Alexander, , "trusting in the strength of the island, and the stores which they had laid up," the strength within and without, of which the prophet speaks.

And Tyrus did build herself - The rock on which Tyre was built was strongly fortified; and that she had abundance of riches has been already seen, Ezekiel 28:1, etc.

And Tyrus did build herself a strong hold,.... Tyre was built upon a rock, and was a strong fortress itself, from whence it had its name; and, besides its natural defence, it had a wall one hundred and fifty feet high, and its breadth was answerable to its height (e); but yet, as it could not defend itself against Alexander the great, who took it; so neither against the Gospel of Christ, which found its way into it, and was mighty to pull down strong holds in a spiritual sense:
and heaped up silver as the dust, and fine gold as the mire of the streets; the riches of these cities, especially Tyre, are often made mention of; they were famous for their wealth, being places of great trade and merchandise; see Isaiah 23:2 all which were to be holiness to the Lord, and for the sufficient feeding and durable clothing of them that dwell before him, Isaiah 23:18 his ministers.
(e) Arrian. de Exped. Alex. l. 2. c. 21.

The heathen historian, DIODORUS SICULUS [17.40], confirms this. "Tyre had the greatest confidence owing to her insular position and fortifications, and the abundant stores she had prepared." New Tyre was on an island seven hundred paces from the shore. As Isaiah's and Ezekiel's (Ezekiel. 27:1-36) prophecies were directed against Old Tyre on the mainland and were fulfilled by Nebuchadnezzar, so Zechariah's are against New Tyre, which was made seemingly impregnable by a double wall one hundred fifty feet high, as well as the sea on all sides.