I'm sure it's put various ways, I remember how Dr. Laura Schlessinger would say it after talking to someone on the phone. Someone would make a revealing comment about themself, and she'd pick up on that, and caution us that when someone does this, don't just whitewash it. People say these sorts of things about themselves because that's how they see themselves, and we do well to pay attention.I think it is a quote that says: when someone SHOWS you who they are, believe them the first time.
Much love!