Therefore you shall be perfect, just as your Father in heaven is perfect. (Matthew 5:48)
The Sermon on the Mount is often regarded as merely a code of morality, which may be isolated with advantage from the metaphysics of the Christian creed. But if we regard the Sermon on the Mount as merely a moral code we are at once struck by its intense, its impracticable, idealism. “Blessed are the poor in spirit;” “Judge not;” “Be ye perfect,”—these and the like commandments, however much they may have been anticipated in India, or practiced by Essene recluses, or thought out independently by Stoics here and there, are in too defiant contradiction of the apparent laws of social progress ever to have commanded the assent of the most practical portion of our race, except in the conscious assurance of a superhuman law under the human paradox, a Divine power under the human life. And it is to this assurance that the whole of the Sermon on the Mount appeals. “Be ye perfect, even as your Father in heaven is perfect.” It puts before us an absolutely perfect Being as the ultimate standard for our conduct, consecrating all our ideal aspirations, by assuring us that they are not the mere mental fringes of our experience as it fades into unknown space, but justifiable appropriations by anticipation of a reality now outside us, but in time destined to be ours.
Christianity not only provides us with an absolute end for conduct, which, as being real, makes our moral ideals speculatively justifiable, but it provides us with an adequate knowledge of that end in the teaching and character and life and death of Jesus Christ—that is, with a standard for conduct which, as having been realized in human history, makes our moral ideals practically possible. If the Sermon on the Mount had been and remained a code of ethics, written upon tables of stone, it might have been liable to the charges of inadequacy and exaggeration which have so often been brought against it. But in the face of the life of Jesus Christ it is willful perversity to call the Sermon on the Mount exaggerated. In the face of the fruits of His death it is impossible to call it inadequate, or to deny that the gradual amelioration of our servile, our domestic, our social, our political, our intellectual, our moral life was all contained by implication in the precept, “Be ye perfect,” and has been wrought out under the influence of the Christian faith in obedience to the Christian sanction.