“I rise only to say that I do not intend to say anything.”

The Moment of the Storm (p. 181)
Short fiction, The Doors of His Face, The Lamps of His Mouth, and Other Stories (1971)

Act I (p. 40)
The Trial of God (1979)

I, 32, reported in Bartlett's Familiar Quotations, 10th ed. (1919). Compare: "I do not love thee, Doctor Fell, / The reason why I cannot tell; / But this alone I know full well, / I do not love thee, Doctor Fell", Tom Brown, Laconics.
Epigrams (c. 80 – 104 AD)

Letter on the China Root, quoted in O'Malley 1964, p. 201

after announcing his Alzheimer's diagnosis. http://edition.cnn.com/2007/SHOWBIZ/books/12/13/terry.pratchett
Misc

Associated Press interview, , quoted in [2014-11-19, Bill Cosby on Rape Allegations: ‘I Don’t Talk About It’, Maya Rhodan, Time, http://time.com/3596545/cosby-responds-rape-allegations-ap-video/, 2014-11-24]
Post-interview on-camera remarks, requesting they not air his interviewer's attempt to ask him about comedian Hannibal Buress' comedy routine about multiple women having alleged that Cosby drugged and raped them:
Brett Zongker: I have to ask about your name coming up in the news recently regarding this comedian—
Bill Cosby: No, no, we don't answer that.
Brett Zongker: OK. I just wanted to ask you if you wanted to respond about whether any of that was true.
Bill Cosby: There's no response.
Brett Zongker: I'm gonna ask you, if— With the persona that people know about Bill Cosby, should they believe anything differently about what—?
Bill Cosby: There is no comment about that.
Brett Zongker: OK.
Bill Cosby: And I'll tell you why.
Brett Zongker: OK.
Bill Cosby: I think you were told. I don't want to compromise your integrity, but um, we don't— I don't talk about it.

This is the Truth! (1949)
Context: I was responsible only for Joe Jackson. I positively can't say that I recall anything out of the way in the Series. I mean, anything that might have turned the tide. There was just one thing that doesn't seem quite right, now that I think back over it. Cicotte seemed to let up on a pitch to Pat Duncan, and Pat hit it over my head. Duncan didn't have enough power to hit the ball that far, particularly if Cicotte had been bearing down. Williams was a great control pitcher and they made a lot of fuss over him walking a few men. Swede Risberg missed the bag on a double-play ball at second and they made a lot out of that. But those are things that might happen to anybody. You just can't say out and out that that was shady baseball.

'MR. DELLINGER: Yes . . . and I hope you will do me the courtesy not to interrupt me while I am talking.'
THE COURT: I won't interrupt you as long as you are respectful.
'MR. DELLINGER: Well. I will talk about the facts and the facts don't always encourage false respect.'
United States of America vs. David T. Dellinger et al.