This is a statement found in prophecies detailing the downfall of Tyre and Sidon. These Phoenician cities had been centers of trade and commerce for the Mediterranean world. They were unbelievably wealthy and quite full of themselves. They had a history of wealth and influence. Phoenician traders sailed the seas and caravaned the land to carry the wealth of empires across the known world that Israel was linked to in the ancient Middle East.
God saw the pride of Tyre and Sidon. Along with commerce, the Phoenicians spread culture, and one of the more insidious cultural trade items was idolatry. The Phoenicians on more than one occassion had been the source of spiritual apathy to Israel. They had been responsible for Israel turning away from God. And God was bringing judgment upon the Phoenicians for their proud idolatry. Assyria would render them non-important. Their influence would be destroyed. Their vast trading network would become only a memory after this judgment.
God will not let human pride stand against Him. He will show Himself to be sovereign in everything. It is best to realize this and to humbly submit to His will in all things.