Why was it that God made two Covenants--not one, and not three? Because there were two parties concerned. In the First Covenant man was to prove what he could do, and what he was. In the Second, God would show what He would do. The former was the time of needed preparation; the latter, the time of Divine fulfillment. The same necessity as there was for this in the race, exists in the individual too. Conversion makes of a sinner a child of God, full of ignorance and weakness, without any conception of what the whole-hearted devotion is that God asks of him, or the full possession God is ready to take of him. In some cases the transition from the elementary stage is by a gradual growth and enlightenment. But experience teaches, that in the great majority of cases this healthy growth is not found. To those who have never found the secret of a healthy growth, of victory over sin and perfect rest in God, and have possibly despaired of ever finding it, because all their efforts have been failures, it has often been a wonderful help to learn that it is possible by a single decisive step, bringing them into a right relationship to Christ, His Spirit, and His strength, to enter upon an entirely new life.
What is needed to help a man to take that step is very simple. He must see and confess the wrongness, the sin, of the life he is living, not in harmony with God's will. He must see and believe in the life which Scripture holds out, which Christ Jesus promises to work and maintain in him. As he sees that his failure has been owing to his striving in his own strength, and believes that our Lord Jesus will actually work all in him in Divine power, he takes courage, and dares surrender himself to Christ anew. Confessing and giving up all that is of self and sin, yielding himself wholly to Christ and His service, he believes and receives a new power to live his life by the faith of the Son of God. The change is in many cases as clear, as marked, as wonderful, as conversion. For lack of a better name, that of A Second Blessing came most naturally.
When once it is seen how greatly this change is needed in the life of most Christians, and how entirely it rests on faith in Christ and His power, as revealed in the Word, all doubt as to its scripturalness will be removed. And when once its truth is seen, we shall be surprised to find how, throughout Scripture, in history and teaching, we find what illustrates and confirms it.
My own commentary: Murray is not preaching a "second blessing" as was taught by Wesley, that is, an event in the life of a Christian after which the Christian walks in sinless perfection without interruption. He (Murray) is teaching a walk of faith in Christ to live the Christian life moment by moment in and through the Christian. I myself bristle anytime I hear that term "second blessing".