The results of holiness are desirable. These are matters of experience. They can never be appreciated without experience. We begin to realize them at conversion when the work of holiness begins. Happiness is felt which no tongue can describe, arising partly out of relief from the enormous burden of sin, from the deep consciousness of guilt, from a terrible sense of the wrath of God, from the awful fear of punishment — happiness produced in part by the contrast which the soul feels between a state of pardon and a state of condemnation. But, besides all this, there are the beginnings of a new and spiritual life. The present manifest workings of the Holy Spirit upon the heart and the feeling of inward renovation are all suited to the constitution of the soul. Where the power of inward depravity is broken, and the feelings, motives, and will are brought into harmony with the will of God, inward comfort and joy are the natural results. And there is happiness in faith; for we are formed to believe; — to trust implicitly in God; and the manifestation of a Redeemer, suits precisely this propensity to confide in a power able to support and to ransom us. This is the rest of the soul. In unbelief, it is "like the troubled sea," agitated, weary, away from home, incapable of repose. In faith, the soul is at home, and must be happy. And there is happiness in love. We were made to love. The malevolence of sin is its principal virus. No man can be happy with a consciousness of hate within him. Hatred to God, to man, even to an enemy, will make the noblest soul upon earth the home of wretchedness. Love harmonizes with a sense of duty — with the primary fundamental laws of the soul; and he who first feels the gentle, sweet, subduing power of love can hardly fail to rejoice. To all really converted we may say, "Whom [Jesus] having not seen ye love. In whom, though now ye see him not yet believing, ye rejoice with joy unspeakable and full of glory." And then there is bliss imparted — direct, rich beyond description, from the resident God within the converted soul, bliss which is designed to increase forever.
But what Christian does not know that this inward joy meets with sad interruptions from the rising power of inward depravity? This, it cannot be denied, disturbs the moral harmony upon which happiness depends, renders it irregular and uncertain in proportion to its amount and force. And to give permanence and certainty to the bliss of conversion, it must be totally removed. If it were to be always kept under, if as a source of temptation it were never to gain the mastery, the enjoyments of the soul, great as they are, would be far less than in a state of perfect purity. If salvation in part — if the beginnings of sanctification are capable of producing so much substantial joy; how much more may be realized when the work is complete? This is clear from a priori evidence, but experience must destroy every vestige of doubt. The deep, pervading, elevating and abiding joy in the state of entire sanctification is known, is matter of fact which both really and comparatively shows how desirable it is to be holy.
The power to glorify God is fearfully impaired by indwelling sin. The sad accusations of conscience, of history, and of revelation against believers, are in evidence of this. Sin utterly destroyed — the soul athirst for God and swallowed up in his love, and the divine glory then rises above every other consideration in earth or heaven. With what clearness and force can the soul wholly cleansed, glorify God by reflecting his image, by presenting truthfully his power to save, by showing the divine reality — the superhuman strength of experimental godliness. How conclusively it refutes all cavil in regard to experimental religious verities, silences infidelity, and dissipates fear by the indubitable evidence of fact which all men can see, and no man dispute. This is bringing glory to God by confounding his enemies, by demonstrating his claims and illustrating his living power to save the lost — a style of logic which transcends all the dictations of scholasticism, and leaves nothing to desire. And how potent is the arm which is thus held out to the feeble in virtue! What encouragement to the halting and despairing! The living demonstration of the power of grace lifts up the head that was bowed down to the dust, and the sweet, inspiring language of love invites the timid forward in the way to heaven, with a charm which multitudes are unable to resist. The work of God strengthens and revives; sinners are saved by scores and hundreds, by the living power of perfect love. We have but to suppose the whole church completely redeemed, and burning with love that casts out fear, to have some idea of the power in this experience to promote the glory of God. Who doubts — who can doubt that the aggressive energy of the church would then be in a high sense irresistible, and that the earth would soon "be full of the knowledge of the Lord as the waters cover the sea?” The results of holiness! They can never be shown by rhetoric or logic. They cannot be appreciated without trial. We must feel the power of full salvation to know it. We must prove it when we are called to grapple with the monster death; — must enjoy it in the thrill of delight which heaven will bring to the enraptured soul; must see it in the glory that beams from the Triune God in that bright world; — must hear it in the songs and hallelujahs of redeemed ones, and angels, and seraphs, where "the wicked cease from troubling and the weary are forever at rest." Desirable! Ah! if it be desirable to be relieved from all fear — to be elevated to a state of calm and permanent bliss — to be able to glorify God even in the fire — to be ready for death without a moment's warning — to live with God forever, it is desirable to be holy.
— edited from The Central Idea of Christianity (2nd edition, 1867) Chapter 4.