Ever been really thirsty?
You get a glass of crushed ice, pour a cold Diet Dr. Pepper (that’s my favorite) on top.
You believe this will quench your thirst. So there. Thirst quenched? Not hardly.
Believing is more than thinking. It is picking up the glass and drinking.
Belief is not merely an agreement with facts in the head; it is also an appetite for God in the heart, which fastens on Jesus for satisfaction. “He who comes to me shall not hunger and he who believes in me shall never thirst!”
Therefore eternal life is not given to people who merely think that Jesus is the Son of God. It is given to people who drink from Jesus as the Son of God. “The water that I shall give him shall become in him a well of water springing up to eternal life” (John 4:14).
He is also the bread of life, and those who feed on him for nourishment and satisfaction live by him. “I am the living bread that came down out of heaven; if anyone eats of this bread, he shall live forever” (John 6:51).
The point of these images of drinking and eating is to make clear the essence of faith. It is more than believing that there is such a thing as water and food; and it is more than believing that Jesus is life-giving water and food. Faith is coming to Jesus and drinking the water and eating the food so that we find our hearts satisfied in him.
~ John Piper, Future Grace