You ask: “But how do I attain this? And what does the Holy Spirit have to do with me?” Answer: “He baptized me; He proclaimed the Gospel of Christ to me; and He awakened my heart to believe. Baptism is not of my making; nor is the Gospel; nor is faith. He gave these to me. For the fingers that baptized me are not those of a man; they are the fingers of the Holy Spirit. And the preacher’s mouth and the words that I heard are not his; they are the words and message of the Holy Spirit. By these outward means He works faith within me and thus He makes me holy.” Therefore just as we should not deny that we are baptized and are Christians, so we should not deny or doubt that we are holy. It would be good to impress this on the people well and to accustom them not to be frightened or scared by it. I and others, for example, were so deeply steeped in our monkery and unbelief that I was terrified by the thought that a man should consider himself holy on earth or let others call him holy. For our thoughts floated only up there among the deceased saints and blessed ones in heaven, even though in Scripture the word “holy” is always applied to those living here on earth. Thus St. Paul asks in nearly all his epistles that greetings be conveyed to the saints. He says: “All the saints greet you” (2 Cor. 13:13). And in 1 Tim. 5:10 he speaks of the widows who “washed the feet of the saints.” Here he employed the word “saints” freely with reference to all Christians. And in the early Christian Church it was long customary for its members to call one another saints. This custom should still prevail. For it is not arrogant on the part of Christians to call one another holy because of Christ; it is glory and praise to God. For by doing so we are not praising our own stinking work-righteousness; we are praising His Baptism, Word, grace, and Spirit, which we do not have out of ourselves but which have been given to us by Him.
Thus you must learn from this text how and where you are to look for the Holy Spirit—not up above the clouds but in the place to which Christ directs you when He says: “The Comforter whom the Father will send” and “He will teach you all things and bring to your remembrance.” From these words we infer that He does not remain seated up above but is sent down to Christians. And he who is to find and receive Him must not gape upward—as we once did—as though He were flitting about up there among the deceased saints, apostles, martyrs, virgins, etc. No, He is down here on earth, just as Christendom is here on earth. For wherever it is, there He will also be at all times and forever, as Christ said earlier. Thus we must picture Him as being in close association with the office and order of Christendom, the Word and the sacraments. These we must esteem highly and praise, believing that the Holy Spirit is present wherever they are present; and that whoever receives them certainly receives also the Holy Spirit, who works through these means, enlightens the heart, creates the knowledge of Christ or faith, and in this way makes sinners pure and holy. This is our comfort and our trust, that with good reason we may glory and confidently say: “We are holy. We are members of a holy fraternity in Wittenberg, in Rome, in Jerusalem, and wherever holy Baptism and the Gospel are. And we do not regard one another otherwise than as saints of God. Even though we are still sinners and many failings always remain in our flesh and blood, He covers up our sins and impurities. Thus we are accounted entirely pure and holy before God, as long as we cling to Christ and His Baptism and rely on His blood.”
Luther, M. (1999, c1961). Vol. 24: Luther’s works, vol. 24 : Sermons on the Gospel of St. John: Chapters 14-16 (J. J. Pelikan, H. C. Oswald & H. T. Lehmann, Ed.). Luther’s Works (24:170). Saint Louis: Concordia Publishing House.