From the Word
37 And the Father who sent me has himself borne witness to me. His voice you have never heard, his form you have never seen; 38 and you do not have his word abiding in you, for you do not believe him whom he has sent. 39 You search the scriptures, because you think that in them you have eternal life; and it is they that bear witness to me; 40 yet you refuse to come to me that you may have life.
John 5:37–40, RSV
The external word or preaching belongs to Christianity as a channel or means through which we attain unto the forgiveness of sins, or the righteousness of Christ, with which Christ reveals and offers us his grace or lays it in our bosom, and without which no one would ever come to a knowledge of this treasure. Whence would any man know, or in what man’s heart would it ever come, that Christ, the Son of God, came from heaven for our sake, died for us, and rose from the dead, acquired the forgiveness of sins and eternal life, and offers the same to us, without publicly having it announced and preached? Although he acquired this treasure for us through his suffering and death, no one could obtain or receive it, if Christ did not have it offered, presented, and applied. All that he had done and suffered would be to no purpose, but would be like some great and precious treasure buried in the earth, which no one could find or use.
Therefore I have always taught that the oral word must precede everything else, must be comprehended with the ears, if the Holy Ghost is to enter the heart, who through the Word enlightens it and works faith. Faith does not come except through the hearing and oral preaching of the gospel, in which it has its beginning, growth and strength. Therefore the Word must not be despised, but held in honor. We must familiarize ourselves with it and constantly practice it, so that it ever bears fruit. It can never be understood and learned too well.
Here then you have all that belongs to the article of the righteousness of Christ. It consists in the forgiveness of sins, offered to us through Christ, and received by faith in and through the Word, purely and simply without any works on our part. Yet I do not mean that Christians should not do good works, but that these are not to be mingled in the doctrine of faith and decorated with the shameless delusion that they avail before God as righteousness. After we have this righteousness of faith, works are to follow and continue here on earth. Both faith and works are to be maintained, each in its proper place, the former before God above all works, the latter in works of love to our neighbor.
Luther, Martin, and John Sander. Devotional Readings from Luther’s Works for Every Day of the Year. Augustana Book Concern, 1915, pp. 395–96.