Contrary to what many people think, those gigantic power stations that light up our cities don’t store electricity for later use, but rather produce energy to meet the immediate demand. Their huge turbines generate just enough power to meet the demand at any given moment. Each time there is a demand for more, then the plant responds and increases output. So, whenever you turn on an appliance, it literally places a demand on the system and prompts greater output.
And that’s how the Bible describes God’s care for his people. It’s not stored up like finite deposits in a bank which can eventually be exhausted. It is inexhaustible, but only ever comes to us as we need it and to the extent that we need it. “My Grace is sufficient for you,” the Lord says. And prayer is the switch that registers our need.