A new tractate! On rulings that the court issues in error, and people then follow those ruling - are they held accountable, and if so, how? Sources are in Leviticus and Numbers. Plus, Eduyot and Avot. Also, a new mishnah: A decision to violate a mitzvah is in error - who would bring an offering to atone? Also, the communal offering for when the court explicitly allows something that is not permitted. Spotlighting Ben Azzai and Ben Zoma.