Just FWIW, I sent the link below to the person who asked about the "remain
silent" quote. It's a feature by Lewis Lord titled "Looking for Lincoln:
Historians sort through the words others put in his mouth." It makes a
direct reference to the quote in question, and to the fact that there's no
record of anyone hearing Lincoln actually say it. On the web there are 100s
of attributions to Lincoln, 10 or so to Twain, a few to "Anon," 1 each to
Horace and Samuel Johnson, ad a few to scattered other folks.

http://www.usnews.com/usnews/issue/970217/17linc.htm