When a man is speaking to God he is at his very acme. It is the highest activity of the human soul, and therefore it is at the same time the ultimate test of a man’s true spiritual condition. There is nothing that tells the truth about us as Christian people so much as our prayer life. Everything we do in the Christian life is easier than prayer.
Studies in the Sermon on the Mount, Eerdmans, 1971, v. 2, p. 46.