Sin-offerings that could not be offered as sacrifices, and therefore were left to die: 5 cases. A more brutal death, surely, than simply putting it to death.... Also: the korban of "par he'elem davar shel tzibur" (What's What). These sin-offerings, both individual and communal, attest to the need for sin-offerings... Namely, that people sin. Plus, a focus on Temurah - the exchange or substitution of a specific animal - here, comparing the stringencies of the original korban to the substitute, and vice versa.