Sanctification
I. The sanctification of which our Lord speaks in this place, is the consecration of the whole creature, of the whole being, to the spiritual purpose of the service of our heavenly Father. To give up everything in order that His will may be accomplished, to do that will to the very full this is the perfect sanctification of all things. And, of course, this sanctification, in itself, does not necessarily imply any change in the thing which is sanctified. If we think of things which stand at the lowest end, and of things which stand at the highest end of being, there is no change at all in the consecration of either to the fulfilment of the will of God. But when we think of all that stands between these, when we think of the consecration of a finite creature or, still more, of a finite creature, intelligent and possessed of will, and yet the evil in that will it is plain that the consecration, of necessity, must imply a real change in the thing that is consecrated. If there is evil, that evil cannot be dedicated to God; if there is anything which hinders the service of our Father, that hindrance must be taken away.
II. In all work that has to be done for the sake of God here among men, the same unchanging rule ever prevails; and the man who would undertake to do it, must himself begin in his own person that regeneration which he is desirous to produce in others, and must begin to sanctify himself. If he is to help others to sanctify themselves, if he is to be the source of any moral and spiritual growth, it must be because there is in him the same moral and spiritual growth, and he must derive it from the source of all moral and spiritual growth the sanctification of the Lord Jesus Himself. It is only by beginning within, and by seeking to be what He was, that it is possible for us to do His holy work; and those who desire to be a blessing to their fellowmen must copy the words of the Lord, and since it is their sanctification that is really needed, they must begin by sanctifying themselves.
Bishop Temple, Christian World Pulpit,vol. xxix., p. 82.
References: John 17:19. F. W. Robertson, Sermons,2nd series, p. 204; E. Bersier, Sermons,1st series, p. 120; John 17:20; J. H. Thom, Laws of Life after the Mind of Christ,p. 18. John 17:20; John 17:21. Spurgeon, Sermons,vol. xii., No. 668; H. W. Beecher, Christian World Pulpit,vol. ix., p. 376; R. Thomas, Ibid.,vol. x., p. 112.