"This is that mystery which is rich in divine grace to sinners: wherein by a wonderful exchange our sins are no longer ours but Christ's, and the righteousness of Christ not Christ's but ours. He has emptied himself of his righteousness that he might clothe us with it and fill us with it; and he has taken our evils upon himself that he might deliver us from them."
"Learn Christ and him crucified. Learn to pray to him and, despairing of yourself, say, 'Thou, Lord Jesus, art my righteousness, but I am thy sin. Thou hast taken upon thyself what is mine and hast given to me what is thine. Thou hast taken upon thyself what thou wast not and hast given to me what I was not.'"
Martin Luther, quoted in J. I. Packer and Mark Dever, In My Place Condemned He Stood, page 85, footnote 31.