trough or spring?

I read this amazing quote today:

God has no needs that I could ever be required to satisfy. God has no deficiencies that I might be required to supply. He is complete in Himself. He is overflowing with happiness in the fellowship of the Trinity. The upshot of this is that God is a mountain spring, not a watering trough. A mountain spring is self-replenishing. It constantly overflows and supplies others. But a watering trough needs to be filled with a pump or bucket brigade. So if you want to glorify the worth of a watering trough you work hard to keep it full and useful. But if you want to glorify the worth of a spring you do it by getting down on your hands and knees and drinking to your heart's satisfaction, until you have the refreshment and strength to go back down into the valley and tell people what you've found. You do not glorify a mountain spring by dutifully hauling water up the path from the river below and dumping it in the spring. What we have seen is that God is like a mountain spring, not a watering trough. And since that is the way God is, we are not surprised to learn from Scripture...that the way to please God is to come to Him to get and not to give, to drink and not to water. He is most glorified in us when we are most satisfied [by] Him.

hi dadMy hope as a desperate sinner, who lives in a Death Valley desert of unrighteousness, hangs on this biblical truth: that God is the kind of God who will be pleased with the one thing I have to offer--my thirst.

[John Piper, The Pleasures of God, pp. 215-216]
emphasis mine