"No sins dare and can remain upon Christ. Such faith makes me pure and acceptable to the Father. Of this faith the pope and our highly educated leaders know nothing to speak, much less to believe. They teach that man should do many good works if he is to be acceptable to God and be free from sin, and that then God imparts to him his grace.
However, here the Lord speaks quite differently, and says: “The Holy Spirit will convict the world in respect of sin, because they believe not on me.” Unbelief only is mentioned here as sin, and faith is praised as suppressing and extinguishing the other sins, even the sins in the saints.
Faith is so strong and overpowering that no sin dare put it under any obligation.
Although sins are present in pious and believing persons, they are not imputed to them, nor shall their sins condemn them.
This is Paul’s meaning when he says in Romans 8:1: “There is therefore now no condemnation to them that are in Christ Jesus, who walk not after the flesh, but after the Spirit.” Their hearts are cleansed by faith, as Peter writes in Acts 15:9.
Therefore, whatever they do in this faith, in this assurance is all good, pure and pleasing to God. On the contrary, without this faith all their doings are sin and destruction, though their good works may shine and glitter as beautifully as they will, and even though they raise the dead.
For Paul says: “Whatsoever is not of faith is sin,” Romans 14:23.
What will now become of all the priests, nuns and monks who, wishing to escape sin, run into cloisters and undertake to do many good works without this faith?
Unbelief is called sin, as I said, but to believe on Christ — that he takes my sins upon himself, reconciles me to the Father and at the same time makes me his heir of all that is in heaven and earth — this is good works.
In John 6:28-29, the Jews asked Christ: “What must we do, that we may work the works of God?” Jesus answered: “This is the work of God, that ye believe on him whom he hath sent.”
Yea, and should we preach thus, who will then enter the cloisters or contribute anything for them? The purses of the monks would then surely become flat, their kitchens scanty, their cellars empty and neglected.
For this reason they will not allow faith to be preached; nay, they condemn this doctrine and banish its preachers."
--Martin Luther, from one of the sermons for the Fourth Sunday after Easter