“We're safe," said Ford, after his first ever teleport transfer (and discovering that he and Arthur had been transported onto the bridge of an enemy space ship). "Ah," said Arthur, "this is obviously some strange usage of the word 'safe' that I wasn't previously aware of."
--Douglas Adams, The Hitchhiker's Guide to the Galaxy
The Spring of Gihon lies on the eastern flank of Mount Zion and, in Hezekiah's day, lay outside the walls of Jerusalem. Foreseeing a siege by the Assyrian army, and believing that the location of the spring was the city's weak point, Hezekiah drove a shaft from the spring through solid rock and directed the water inside the walls to the Pool of Siloam. He then closed off the "old pool" (the pool of the spring Gihon) and built a second wall to enclose it. Thus Hezekiah made Jerusalem safe.
Isaiah observed: "You made a reservoir between the two walls for the water of the old pool. But you did not look to its Maker, nor did you have respect for Him who fashioned it long ago." The irony of the project, according to the prophet, was that God, who fashioned the spring long ago, deliberately placed it outside the walls. Its location was divinely designed to make Jerusalem weak and vulnerable. Weakness was God's will for the city.
As it turned out, Hezekiah's walls and water system were wasted time and effort. God delivered the city in a way that had nothing to do with their endeavor. You can read the story for yourself in 2 Chronicles 32.
Here again is the abiding principle that God creates weakness in us that we may become strong. Our physical, mental, social, and emotional limitations were fashioned long ago that we may know our Lord's abiding, boundless strength.
Therefore, we can never say of anything God asks us to do, "It is too hard for me," for our weakness, when acknowledged, brings us to prayer and into the presence of God's infinite power. Our weakest points become our strength, if we have regard for him who fashioned those weaknesses long ago.
Paul, who was fond of paradox, put it this way: "When I am weak then I am strong." We're most safe when we're most vulnerable--a "strange usage of the word 'safe,'" I must say.
 Cf., 2 Chronicles 32:20
 Isaiah 22:11
 It was, in fact, the means by which David gained access to the old Jebusite citadel of Jerusalem when it was in the hands of the Canaanites (2 Samuel 5:6-10).
 2 Corinthians 12:10