"Christ Dwells In Sinners. Martin Luther: Now I would like to know whether your soul, tired of her own righteousness, would learn to breathe and confide in the righteousness of Christ. For nowadays the presumption besets many, especially those who with all their powers try to be righteous and good. They do not know the righteousness of God, which is most bountifully and freely given to us in Christ, and so they seek to do good in and by themselves until such a time as they feel confident that they can stand before God adorned with their own virtues and merits, but this cannot possibly be done. You yourself were of this opinion, or rather error, and so was I, and even now I fight against this error and have not yet conquered it.
Therefore, my dear brother, learn Christ and him crucified, learn to pray to him, despairing of yourself saying: "You, Lord Jesus, are my righteousness, but I am your sin; you have taken on yourself what you were not, and have given to me what I was not." Beware of ever aspiring to such purity that you do not want to seem to yourself, or to be, a sinner. For Christ dwells only in sinners.
It was for this that he came down from heaven, where he dwelled in the righteous, that he might also dwell in sinners. Think about his love and you will see how beautifully it will comfort and sustain you. For if it is only our own efforts and strivings that can achieve a quiet conscience, what did he die for? You will therefore find peace only in him, in faith despairing in yourself and your own works; and thus you will learn that as he took you up and made your sins his own, he made his righteousness yours. LETTER TO GEORGE SPENLEIN (April 8, 1516)" pg. 54 'Romans 1-8' New Testament VII Reformation Commentary On Scripture