“Silence is the only language god speaks.”

Bk. XIV, ch. 1
A paraphrase of the last portion of this has sometimes been cited as a quotation of Melville: God's one and only voice is silence.
Pierre: or, The Ambiguities (1852)

Attributed to Bonhoeffer on the Internet, and supposedly from Bonhoeffer: Pastor, Martyr, Prophet, Spy http://books.google.com/books?id=aG0q3X8TVpsC&pg=PA486#v=onepage (2010) by Eric Metaxas; however, there is no actual reference in that book. However, in advertising the book Metaxas does state on his site that the quote is from Bonhoeffer. http://ericmetaxas.com/books/bonhoeffer-pastor-martyr-prophet-spy/ First attributed to Bonhoeffer in Explorations 12:1 (1998), p. 3, as referenced by James Cone (2004) Theology's Great Sin: Silence in the Face of White Supremacy, Black Theology, 2:2, 139-152, footnote 1 http://dx.doi.org/10.1558/blth.2.2.139.36027
Compare "Not to Act, is to Act!" by Francis W. McPeek http://www.ergo-sum.net/pics/McPeek.jpg, The Missionary Herald at Home and Abroad, v.141-142 (1945-1946), "Missionary herald, 1945 - Congregational churches," pp.34-35 (We must realize that church inaction is a form of political action, and it is altogether negative. “Not to act, is to act.”)
Misattributed

Source: The Monkey Grammarian (1974), Ch. 4
Ch. 4 -->
Context: Fixity is always momentary. But how can it always be so? If it were, it would not be momentary — or would not be fixity. What did I mean by that phrase? I probably had in mind the opposition between motion and motionlessness, an opposition that the adverb always designates as continual and universal: it embraces all of time and applies to every circumstance. My phrase tends to dissolve this opposition and hence represents a sly violation of the principle of identity. I say “sly” because I chose the word momentary as an adjectival qualifier of fixity in order to tone down the violence of the contrast between movement and motionlessness. A little rhetorical trick intended to give an air of plausibility to my violation of the rules of logic. The relations between rhetoric and ethics are disturbing: the ease with which language can be twisted is worrisome, and the fact that our minds accept these perverse games so docilely is no less cause for concern. We ought to subject language to a diet of bread and water if we wish to keep it from being corrupted and from corrupting us. (The trouble is that a-diet-of-bread-and-water is a figurative expression, as is the-corruption-of-language-and-its-contagions.) It is necessary to unweave (another metaphor) even the simplest phrases in order to determine what it is that they contain (more figurative expressions) and what they are made of and how (what is language made of? and most important of all, is it already made, or is it something that is perpetually in the making?). Unweave the verbal fabric: reality will appear. (Two metaphors.) Can reality be the reverse of the fabric, the reverse of metaphor — that which is on the other side of language? (Language has no reverse, no opposite faces, no right or wrong side.) Perhaps reality too is a metaphor (of what and/or of whom?). Perhaps things are not things but words: metaphors, words for other things. With whom and of what do word-things speak? (This page is a sack of word-things.) It may be that, like things which speak to themselves in their language of things, language does not speak of things or of the world: it may speak only of itself and to itself.

Source: A Soldier of the Great War

Source: Monolingualism of the Other: or, The Prosthesis of Origin