The study provides an in-depth exploration of Luther's understanding of the relationship between the Church and the Holy Spirit. Emphasis is placed on the Lutheran idea of the Church's absolute dependence on the actions of the Spirit, articulated within the Trinitarian framework of the theology of justification by faith. Through the analysis of the Great Catechism, particularly the commentary on the third article of the Creed, the study highlights the originality of Luther's approach to the topic in question. This approach involves interpreting the link between the Church and the Spirit, ecclesiology and pneumatology, from the perspective of an original theology of Revelation. This perspective illuminates the Church as a "complex reality", evolving through the action of the Trinity, through which, in the Spirit, the eternal Word of the Creator is made present among the holy community.