Luther deliberately reorganized the creedal material, without altering the wording, by reducing the twelve articles (corresponding to the twelve apostles) common in the late Middle Ages to the three articles common in the early church. More than a desire for historical accuracy on Luther’s part accounts for this rearrangement. He wanted to concentrate the catechumen’s attention on the saving work of the triune God and further emphasize the pro nobis character of God’s work “for us” in all aspects of our life.
“Luther on the Creed,” by Charles P. Arand, in The Pastoral Luther, ed. Timothy J. Wengert. Grand Rapids: William B. Eerdmans Publishing Company, 2009, p 148.