What does Isaiah 22:11 mean?
The Assyrians—or the Babylonians, if Isaiah is looking forward in time—intended to take Jerusalem by force. Everyone knew their enemy's first strategy would be to lay siege to the city. Isaiah has been listing everything the king and the people did to prepare for that siege (Isaiah 22:8–10).The people of Jerusalem inspected and distributed the weapons. They checked the walls for breaches. They redirected springs from outside the city walls to flow inside the city so they would not run out of water. They tore down homes between the inner and outer walls for the safety of the citizens. This building material was then used to repair the breaches in the wall.
Now Isaiah adds that they made a reservoir of water between these two inner and outer walls. This may have served the purpose of adding another obstacle for enemies who managed to get through the wall. It could have also provided a back-up water supply for the city.
The prophet doesn't fault the king or people of Jerusalem for any of these practical actions. It makes sense to physically prepare for an enemy invasion. What he does fault them for is not looking to the Lord for help. The people were so focused on what they could do tangibly that they didn't ask the Lord to do what He could for them. God's people continue to make the same mistake today, demonstrating lack of faith by not asking God for help when we need it the most.
This statement is concluded by declaring that the Lord planned this siege long ago. It is no surprise to Him. What He wants is for His people to trust Him. The Lord God again wants His people to rely on Him alone. And yet His people will continue to look to other nations and their gods for their salvation.
Commentators who believe Isaiah is pointing forward to Babylon's destruction of Jerusalem find support in this verse. King Hezekiah, himself, did look to the Lord when the Assyrians were coming (Isaiah 37:14–20). That may contrast with this verse, where Isaiah is clarifying that the people did not look to the Lord.