John Calvin Commentary Isaiah 41:18

"I will open rivers on the bare heights, and fountains in the midst of the valleys; I will make the wilderness a pool of water, and the dry land springs of water." — Isaiah 41:18 (ASV)

And 19. I will open rivers. He illustrates the former doctrine in a different manner: namely, that God has no need of outward and natural means for aiding His Church, but has at His command secret and wonderful methods by which He can relieve their necessities, contrary to all hope and outward appearance.

When no means of relief are apparent, we quickly fall into despair and scarcely venture to entertain any hope, except insofar as outward aids are presented to our eyes. Deprived of these, we cannot rest on the Lord.

But the Prophet states that especially at such times they should trust, because then the Lord has more abundant opportunities to display His power, when people perceive no ways or methods, and everything appears to be utterly desperate.

Contrary, then, to the hope and belief of all people, the Lord will assist His people, so that we are not driven back and forth by doubt and hesitation.

On lofty mountain tops. In order to confirm His statement more fully, He promises that He will perform miracles contrary to the nature and order of things, so that we do not imagine that we should think and judge these things according to human capacity, or limit the power and promises of God to these inferior means.

The Lord has sufficient power in Himself, and does not need to borrow from any other, and is not confined to the order of nature, which He can easily change whenever He sees fit; for when He says that He will make waters flow on the tops of mountains, and fountains in valleys, and pools in deserts, we know that all this is contrary to the order of nature.

The reason why He promised these things is abundantly evident. It was so that the Jews would not think that they were prevented from returning to Judea by that vast desert in which travelers are scorched by the heat of the sun and deprived of all the necessities of life. The Lord therefore promises that He will supply them with water and with everything else that is necessary for the journey.

Now, these things were fulfilled when the Lord brought His people out of Babylon, but much more abundantly when He converted the whole world to Himself by Christ the Redeemer, from whom flow, in great abundance throughout the whole world, waters to quench the thirst of poor sinners. At that time, such a change took place as could never have entered into the imaginations of people.