What does Isaiah 23:15 mean?
Isaiah has written the final word on the destruction of the city of Tyre. It will happen and it is coming. He has called for all who depend on her and honor her to mourn and wail (Isaiah 23:14). He has made it clear that the Lord who will destroy her and Sidon as an act of judgment. This reckoning will be due to Tyre's pride and the false honor heaped upon her by others (Isaiah 23:9).Tyre will be fully and utterly incapacitated. Alexander the Great succeeded in wiping Tyre out in 332 BC. The city was also conquered by the Assyrians, and the Babylonians well before that. It is unknown, exactly, to which destruction in Tyre's future Isaiah is pointing. What is clear is that it will put Tyre out of commission as a functioning and independent seaport for seventy years.
The city will be "forgotten." The prophet means that shippers from other nations won't even consider taking their goods to and through Tyre during that time. Since Isaiah describes those seventy years "as the days of one king," some commentators speculate that he may not have had an exact number of years in mind. Commentators suggest that Isaiah uses seventy 70 years as a way of saying a long time, using the time a long-lived king might reign over a nation.
That season will end, though. Tyre will again begin to thrive as a center of trade, shipping, and prosperity. Yet Isaiah does not describe this return to prominence as a glorious victory. Rather, it is like a prostitute coming out of retirement (Isaiah 23:16). This is not a return to form to Tyre's glory days.