Found on Cyberbrethren — one of his “Daily with Luther” posts:
Whoever wants to be proof against that and be safe must take this admonition to heart and be warned to retain and cling to this Word which Paul proclaimed and to ignore whatever objections others might raise to it, even though these may boast of their side of the story and lend it a good appearance. For here you hear what fruit this Gospel of St. Paul produced among them and what fruit it still produces, namely, that all became Christians through it and were saved and that people must still be saved by it. And since this fruit is ours by virtue of the Gospel, why should we search further or permit ourselves to be diverted from this and be directed and led to other things? For whatever directs us otherwise can surely not be as good, but it must be false and sheer seduction, since it pretends to have something which we already have by means of this Gospel; and thereby it denies all this or disdains it utterly. Therefore Paul addresses the Corinthians as though it were unnecessary to admonish them beyond asking them to recall and observe what they received and how they became Christians. “For if you note that,” he wants to say, “you will surely adhere to it and remain safe from all sorts of error. For you can easily differentiate between my doctrine and theirs and judge in accordance with what you gain from each, observing whether they are able to submit something better than my Gospel, by which you are saved.” And let us note here that Paul is speaking of the oral presentation of the Gospel preached by him and that he assigns to it such a claim and such praise, that they “stand in it and are saved by it” alone. This is clone in contrast to our blind spirits who disdain the external Word and Sacrament, and in their stead adduce their own imaginary spiritism.
Martin Luther, Luther’s Works, Vol. 28: 1 Corinthians 7, 1 Corinthians 15, Lectures on 1 Timothy, ed. Jaroslav Jan Pelikan, Hilton C. Oswald and Helmut T. Lehmann, 1 Co 15:1–2 (Saint Louis: Concordia Publishing House, 1999).