A heart for the glory of God and a heart of mercy for the nations make a Christian missionary. These must be kept together. If we have no zeal for the glory of God, our mercy becomes superficial, man-centered human improvement with no eternal significance. And if our zeal for the glory of God is not a reveling in his mercy, then our so-called zeal, in spite of all its protests is out of touch with God and hypocritical.
—John Piper, Let the Nations Be Glad