In short, the Word and the Holy Spirit, who prepares us for prayer, are in God’s power. It is the Word which we believe—this is what makes our hearts so bold that we dare to call ourselves the children of the Father. Where does this come from? The answer is: From God, who teaches us to pray in the Lord’s Prayer and puts into our hands the book of Psalms. For if we prayed without faith, this would be to curse twice over, as we learned in our nasty papistical holiness. But where there is a believing heart and that heart has before it the promise of God it quite simply and artlessly prays its “Our Father” and is heard. Outside of this church of God you may present your prayers and supplications to great lords and potentates to the best of your ability, but here you have no ability to pray except in Christ Jesus, in order that we may not boast that we are holy as they do in the papacy, who protest, of course, and say: Oh, it would be a presumption for anybody to call himself holy and fit; and yet they teach that man of himself has a “certain preparation” for prayer.
They also teach prayer according to this doctrine in their chants and say: I have prayed in despair as a poor sinner. Oh, stop that kind of praying! It would be better to drop such praying altogether if you despair. For despair ruins everything and if you go to baptism, prayer, and the sacrament without faith and in despair, you are actually mocking God. What you should quickly say, however, is this: I am certain that my dear God has so commanded and that he has assured me of the forgiveness of sins; therefore I will baptize, absolve, and pray. And immediately you will receive this treasure in your heart. It does not depend on our worthiness or unworthiness, for both of these can only make us despair. Therefore do not allow yourself by any means to be driven to despair. For it is a mockery of God when we do not believe the words, “Go and baptize” [Matt. 28:19], that is, baptize those who repent and are sorry for their sins. Here you hear that this is not human work, but the work of God the Father; he is the Householder who wills to dwell here. But if we despair, then we should stay away from the sacrament and from prayer, and first learn to say: All right, it makes no difference that I am unworthy, God is truthful nevertheless, and he has most certainly promised and assured us; I’ll stake my life on this” (Luther’s Works, Volume 51, p.307-308).