“Luther always wrote that Baptism removes the guilt of original sin, although the material of sin, as they call it, viz., concupiscence, remains.”*
Nope. Original sin in the Augustinian sense is total rubbish. Scripture doesn’t know it and Augustine made it up out of his own fevered and delirious mind. And if you turn to Psalm 51 you need to read the Hebrew text and not the Vulgate and its heir, the KJV.
Luther was bright, but he was a Papist about baptism, and thus wrong.
*Heinrich Schmid, The Doctrinal Theology of the Evangelical Lutheran Church, Verified from the Original Sources (trans. Charles A. Hay and Henry E. Jacobs; Second English Edition, Revised according to the Sixth German Edition.; Philadelphia, PA: Lutheran Publication Society, 1889), 257.