What is it about Christians that makes them the salt of the earth and the light of the world? It is not wealth. The desire for wealth and the pursuit of wealth tastes and looks just like the world. Desiring to be rich makes us like the world, not different. At the very point where we should taste different, we have the same bland covetousness that the world has. In that case, we don’t offer the world anything different from what it already believes in.
The great tragedy of prosperity preaching is that a person does not have to be spiritually awakened in order to embrace it; one needs only to be greedy. Getting rich in the name of Jesus is not the salt of the earth or the light of the world. In this, the world simply sees a reflection of itself. And if they are “converted” to this, they have not been truly converted but only put a new name on an old life.
Excerpted from John Piper’s Let the Nations be Glad