There is a strange law at the heart of Parshat Tazria: a woman who gives birth — who has just done something miraculous and happy — is declared ritually impure and kept away from the Temple. What did she do wrong? Perhaps nothing. Perhaps that's exactly the point.
What's the only sin the Jewish people committed that we were never given forgiveness for? What were the mistaken beliefs that led to the creation of the Golden Calf.