Be innocent or guiltless, as in John's got clean hands; he had nothing to do with it. It is sometimes worded as one's hands are clean, meaning “one has done nothing wrong,” as in Don't look at me—my hands are clean. This metaphor for freedom from wrongdoing dates back to at least 1600.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.