(John 7:38)“Whoever believes in me, as the Scripture has said, ‘Out of his heart will flow rivers of living water.’” Literally, it says, out of his belly. But the point is our inner being, call it belly, heart, soul, spirit. What does this mean?- John Piper,
It means that when you come to Jesus to drink, you don’t just get a single drink, but you get spring, a fountain, a well. You get Jesus. Rivers of water will flow because a River-Maker is in you. That’s the point. You will never have to search again for a source of satisfaction for your soul. Every river that needs to flow for the joy of your soul will flow from Jesus. When you come to him, you get him. And he never leaves.
Via Desiring God