“With respect to the Third Article, Luther struggled long and hard to find a simple catechetical term for what is confessed therein about the Holy Spirit.” Albrecht Peters, (trans. Thomas Trapp), Commentary on Luther’s Catechisms: Creed, (St. Louis: Concordia Publishing House, 2011), p. 34.
At a first reading, the third article seems to have a number of elements that are laid side by side like so many blocks without any unifying theme. Luther settles upon the word “holy” in the name Holy Spirit. This does not refer simply to one or more attributes of the Spirit. Rather, it refers to his office and work. It refers to his activity. The Holy Spirit is the Spirit who makes holy. He is, to coin a word, the Holifying Spirit, or to use a word already coined, the Sanctifying Spirit. With this thread, the beads in the article form a necklace. Each of the elements is a work of the Spirit in his office of making the saints holy. By this catechetical move, the article ceases to be a kitchen sink, cigar box, or grab bag of elements. It becomes a unity depicting the sanctifying office of the Spirit.
Luther selects one word from the third article and organizes his explanation around it. But this article gave him the most difficulty, for the Apostles’ Creed simply says, ‘I believe in the Holy Spirit,’ and then appends a series of five seemingly disconnected items …. It was not readily apparent how all these things related to the Holy Spirit. … He takes the name ‘Holy Spirit’ and focuses on the word ‘holy’ in such a way that the Holy Spirit … becomes the sanctifying Spirit in Luther’s explanation. The theme of the ‘sanctifying Spirit’ enables Luther to weave the five disparate items … into an organic unity based on and centered in the sanctifying work of the Holy Spirit …. Instead of using the word ‘holy’ to describe a personal attribute of the Spirit, Luther uses it to describe what the Holy Spirit does for us and to us!
Charles P. Arand, “Luther on the Creed,” in The Pastoral Luther, ed. Timothy J. Wengert, (Grand Rapids: William B. Eerdmans Publishing Company, 2009), p. 156.
With this single focus, the Small Catechism says:
The Third Article: Sanctification
I believe in the Holy Spirit, the holy Christian church, the communion of saints, the forgiveness of sins, the resurrection of the body, and the life everlasting. Amen.
What does this mean? I believe that I cannot by my own reason or strength believe in Jesus Christ, my Lord, or come to Him; but the Holy Spirit has called me by the Gospel, enlightened me with His gifts, sanctified and kept me in the true faith. In the same way He calls, gathers, enlightens, and sanctifies the whole Christian church on earth, and keeps it with Jesus Christ in the one true faith. In this Christian church He daily and richly forgives all my sins and the sins of all believers. On the Last Day He will raise me and all the dead, and give eternal life to me and all believers in Christ.
This is most certainly true.