For the source text click/tap here: Zevachim 13
To download, click/tap here: PDF
A recurring theme throughout the first perek of Massekhet Zevaḥim has been that some sacrifices will become invalid if there are improper thoughts at the time that they are brought, while other sacrifices will remain valid korbanot, although they will not count towards their purpose and if their owner was obligated to bring that sacrifice, he will have to bring another.
During which activities will improper thoughts affect the sacrifice?
The Mishna on our daf mentions four parts of the avoda – of the sacrificial service – where proper intent is essential .