I. The Psalmist speaks here rather of the mind with which the Son of God should come than of the end for which He should come. He speaks of that obedience, which healed our disobedience, as the cause, the life, the soul, of His sacrifice rather than of the sacrifice itself. He exhibits the Atonement in the act of obedience.
II. It is on this very side that He, our Saviour, sets Himself forth as our example. We, too, as many as have been made members of Him, have been sent into the world to accomplish in ourselves and to discharge in the order of His creation a certain will of God; and in the knowledge and accomplishment of that will lies our salvation and the secret of our predestination.
III. This then is the secret of the choice of life: to learn what, among the manifold duties of His great household, God, in the eternal purpose of His love, willed each one of us to discharge. To have discovered this and to have placed ourselves in that path, conforming ourselves therein to the will of God, is to have taken, by God's grace, a decisive step in the way of salvation. For it is to have chosen the will of God and united our own to His; it is to answer the purpose of God for us; it is to be under the guidance of the All-wise, the protection of the Almighty.
E. B. Pusey, Sermons Preached before the University of Oxford,p. 437.
Reference: Psalms 40:9; Psalms 40:10. Spurgeon, Sermons,vol. xvii., No. 977.