Silence in the face of evil is itself evil: God will not hold us guiltless. Not to speak is to speak. Not to act is to act.

Stephen R. Haynes, Readings and Receptions, in The Oxford Handbook of Dietrich Bonhoeffer (Oxford University Press, 2019), p. 478: "The source of this ‘Bonhoeffer quote’ has been identified as a 1998 Heroes exhibit at the now defunct Liberty Museum in Philadelphia (Throckmorton, 2016). From there it migrated to the back flap of Eric Metaxas’s 2010 biography of Bonhoeffer, from which it made its way onto lists of ‘essential Bonhoeffer quotes’, not to mention countless Twitter and Facebook accounts."

Misattributed to Bonhoeffer: Pastor, Martyr, Prophet, Spy (2010) by Eric Metaxas; there is no actual reference in that book. Previously 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 | Compare "Not to Act, is to Act!" by Francis W. McPeek, 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.”) | Also compare to Robert K. Hudnut, A Sensitive Man and the Christ (Fortress Press, 1971), p. 21: "Not to speak is to speak. Not to act is to act. To do nothing when a house is burning is to do something. It is to let the house burn." | Also see Erich von Dietze, "Hope Does Not Disappoint": Honouring the 70th Anniversary of the Death of Dietrich Bonhoeffer, The Bonhoeffer Legacy: Australasian Journal of Bonhoeffer Studies 3 (1) (ATF Press, 2015), fn 8: "While commonly attributed to Bonhoeffer, the origin of this quote remains uncertain."