"Who would ever have guessed that our salvation does not depend on our prayers, our devotional life, our good deeds in general and even those that may be comprehended under the heading 'religious virtues' in particular? Who would have worked it out that salvation depends on the coming to this earth of the Son of God and on his living in lowliness and humility, 'despised and rejected of men'? Who would have thought that the culmination of all this would have been a death like that of a criminal on a cross? And if he was to die in this way, who would have reasoned that on the third day he would rise again? All this is in the plan of God, a plan that we could never have worked out for ourselves. ... This 'mystery,' says Paul, is 'the mystery of the gospel.' The good news that God has worked out our salvation himself and that it involved the sending of his Son to live in obscurity and to die on a cross is certainly something that is not the product of human ingenuity."
Leon Morris, Reflections on the Letter to the Ephesians, (Grand Rapids: Baker Books, 1994), 212.