Paul here draws a distinction between cleansing ourselves from filthiness and perfecting holiness, and these two, though closely connected and capable of being regarded as being but the positive and negative sides of one process, are in reality different, though in practice the former is never achieved without the latter, nor the latter accomplished without the former. Holiness is more than purity; it is consecration. That is holy which is devoted to God, and a saint is one whose daily effort is to devote his whole self, in all his faculties and nature, thoughts, heart, and will. More and more, to God, and to receive into himself more and more of God.
The purifying which Paul has been enjoining will only be successful in the measure of our consecration, and the consecration will only be genuine in the measure of our purifying. Herein lies the broad and blessed distinction between the world's morality and Christian ethics. The former fails just because it lacks the attitude towards a Person who is the very foundation of Christian morality, and changes a hard and impossible law into love. There is no more futile waste of breath than that of teachers of morality who have no message but Be good! Be good! and no motive by which to urge it but the pleasures of virtue and the disadvantages of vice, but when the vagueness of the abstract thought of goodness solidifies into a living Person and that Person makes his appeal first to our hearts and bids us love him, and then opens before us the unstained light of his own character and beseeches us to be like him, the repellent becomes attractive: the impossible becomes possible, and if ye love Me keep My commandments' becomes a constraining power and a victorious impulse in our lives.