Chapter 2 - with 2 new forms of disqualification: the wrong person or a person with the wrong status bringing the offering -- or bringing it at the wrong time. The mishnah lists the many people who would invalidate the offering just by virtue of who they are or what their status is. And then the Gemara looks to source each of the people who would have invalidated the offering, with an effort to find the precise ones. Plus, the example of the "onen," the acute mourner, if he is the kohen gadol, whose service would invalidate the offering. As sourced in the story of Nadav and Avihu, and Aaron's refraining from offering sacrifices immediately after their shocking deaths.