Pseudo-Luther?

     "The woman’s will, as God says, shall be subject to the man, and he shall be master (Gen. iii. 16); that is, the woman shall not live according to her free-will, as it would have been had Eve not sinned, for then she had ruled equally with Adam, the man, as his colleague.  Now, however, that she has sinned and seduced the man, she has lost the governaunce; and must neither begin nor complete anything without the man; where he is, there she must be, and bend before him as before her master, whom she shall fear, and to whom she shall be subject and obedient."

1888:  Karl Pearson, "A sketch of the sex-relations in primitive and mediæval Germany," The ethic of freethought:  a selection of essays and letters (London:  T. Fisher Unwin, 1888), 425.  A more or less hostile witness?  "This paper was written some time ago," but maybe not then published.  I have not yet found Pearson's source (if he didn't do the "translation" himself).  Note that he does not actually name Martin Luther.  Rather, he attributes these words to the "chief hero" of the Reformation, which destroyed "the cloister life".

     That's the best I've been able to do so far, as I do not have access to the database Luthers Werke.
     Meanwhile, Jeanne Powers, of the Bristol Public Library (VA/TN), wrote the editors of Luther on women:  a sourcebook (Cambridge University Press, 2003)—which, along with the Past Masters database Luther's Works, I had searched—and received from Dr. Merry E. Wiesner-Hanks, Distinguished Professor Emerita of History, University of Wisconsin Milwaukee, the following comments, which I have been given permission to reproduce:

Luther said various things about women's obedience, but I can't remember anything quite like this. If the 1888 work was in English, that means it was a translation done very shortly after the Weimar edition, the authoritative German and Latin edition, began to be published. . . .  So . . . if it is a real Luther quotation, it was taken from an earlier German [or Latin] edition, or from an earlier English translation. But citation standards in 1888 were not what they are today. Finding the source is probably impossible, and it may very well be a paraphrase, or something some author wished Luther had said. 

I would advise whoever set [Jeanne Powers] on the task of finding this, that if she/he wants what Luther said about obedience, [the] better [idea] would be to go to writings that we know for sure to be Luther's. Susan's and my book of Luther's writings on women (Luther on Women: A Sourcebook) has several of them, with complete citations. These are all translations from the Weimar edition, or selections from Luther's Works, the mid-20th century U.S. edition that is generally regarded as authoritative for those who don't read German. (All the translations there were made from the Weimar.) Luther's Works has the complete treatises on marriage. And it's indexed. 

. . . my suspicion is that [the quote is] fabricated. 

. . . I've done some sleuthing on my own about Karl Pearson, as well as looked more closely at the book from which this comes. A brilliant mathematician, free-thinker, and women's right advocate, but also a eugenicist. Based on the footnotes in earlier sections of this essay, he read Luther in German and Latin, but it's not clear what edition he was using. (Or not clear from these pages.)  So this is most likely his translation, but who knows where it comes from? This essay was written at a time when German and English social scientists were postulating that there was "primitive matriarchy" (J.J.Bachofen is the most influential thinker on this; Engels picked it up from him), an idea which this essay repeats. 

I think Pearson has some good advice in the essay itself, when he says on the first page that he doesn't have time to present all the facts for what he is arguing, and that until he can he asks the reader to 'treat this paper as one of fanciful suggestion.'

     My thanks to Jeanne Powers of the Bristol Public Library (VA/TN) for the diversion.