1
general::
Phrase(s): Tell the truth and shame the devil.
Prov. To tell the truth even though you have strong reasons for concealing it. • Jill: Have you been using my computer without asking permission? Jane: Uh . . . no. . . . Jill: Come on, Jane, tell the truth and shame the devil.
McGrawhill's American Idioms And Phrasal Verbs