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.
Parshat Terumah teaches that the materials themselves are not the problem—the difference between the Golden Calf and the Mishkan was not the gold, but whether it was used according to God’s command, reminding us that holiness depends on our choices.