For Luther, a theologian of the cross is brought into a relationship with God not by being lifted up into heaven but by being driven down into the depths in order to undergo a particular experience. As Luther wrote:
“...He is a God who looks into the depths and helps only the poor, despised, afflicted, miserable, forsaken, and those who are nothing, there a hearty love for Him is born… There the Holy Spirit is present and has taught us in a moment such exceeding great knowledge and gladness through this experience.” (LW 21:314)
In Mary’s song, for example, Luther grasped that God turned the world with all its wisdom and power into foolishness and gave us another wisdom and power. This is the meaning of Mary's song, recorded in Luke 1:46-55, when she proclaimed that:
“God has regarded me, a poor, despised, and lowly maiden, though He might have found a rich, renowned, noble, and mighty queen, the daughter and great lords he might have found the daughter of Annas or Caiaphas, who held the highest position in the land. But He let His pure and gracious eyes light on me and used so poor and despised a maiden, in order that no one might glory in His presence, as though he were worthy of this, and that I must acknowledge it all to be pure grace and goodness and not at all my merit or worthiness.” (LW 21:314)
Mary’s proclamation expressed the stark experience of God stripping her of any claims to her own righteousness. In her song, Mary said as much, when she declared that, her low estate was regarded by God, not thereby rewarding her for anything she had done, but because “He has done great things for me…” (Luke 1:47).
This is important to pay attention to because Luther’s work to exposit the Magnificat of Mary was not simply to argue a theological point. His approach to the text was pastoral, not polemical. Luther was writing specifically for the young son of his elector, Frederick. Luther exposited the words of a young woman for the sake of a young man who would soon enough become an elector, bearing the daily experience of “honor, power, wealth, knowledge, a life of ease, and whatever is lofty and great.”
In his exposition of the Magnificat, Luther located the greatest temptation for an earthly ruler: to worship one’s self rather than God, look to the heights rather than into the depths, etc. As he warned:
“…it is not without reason that the Scriptures describe so few kings and rulers who were godly men. On the other hand, no one is willing to look into the depths of their poverty, disgrace, squalor, misery, and anguish. From these, all turn away their eyes. Where there are such people, everyone takes to his heels, forsakes and shuns, and leaves them to themselves; no one dreams of helping them or of making something out of them. And so they must remain in the depths and in their low and despised condition. There is among men no creator who would make something out of nothing.” (LW 21:300)
Luther addressed the sinner not in order to provide a description of a type of theology but instead to confront, in a particular way, the individual person's experience of temptation and sin. The preacher is meant to identify the double work of God: first, that God does a strange work, killing the sinner so that he can accomplish his second, proper work of raising him from death and making him alive in Christ through faith.
This is the reality of God's work for his sinners. His strength lies hidden under apparent weakness. His wisdom hides under apparent folly. His proper work is concealed under his alien work. The future glory of the Christian is hidden under his present sufferings.
The point Luther made, again and again, was that distance between God and sinners is collapsed when the crucified Christ himself comes to sinners through a preacher. For this reason, Luther emphasized the experience of suffering and death, and how faith trusted Christ's promise to never abandon or forsake us. In his formulation of this experience, Luther was expressing nothing other than how God makes a theologian of the cross.
Contrary to the piety of his day, Luther saw that Mary was not the source of goodness and blessedness. She was a sinner, the enemy being overcome so that God could accomplish his work in and through her.
Mary does not point to herself as the well-spring of great and good things for which she had been regarded and blessed by God. Instead, her song summarizes, “In all those great and good things there is nothing of mine, but he who alone does all things, and whose power works in all, has done such great things for me.”
So when God comes to sinners he reverses the direction of suffering, working backward from Christ’s cross to our own and from his suffering to our suffering, to lift it off of us so that he may bear it for us. This is a theme that runs through all of Luther's preaching and teaching including in his commentary of the Magnificat where it's recorded that Mary was brought into a relationship with God through the particular humbling experience of being chosen to be the mother of our God and Savior, Jesus the Christ. As a theologian of the Cross, Mary uses her song not to answer the question, “How do I find a gracious God?”, but instead to preach about how a gracious and loving Father found her.