The second half of the tenth perek of Massekhet Menaḥot focuses on the laws of semikha – laying of hands on the sacrifice. The Mishna on today’s daf teaches that no communal sacrifices include semikha, except for the unique se’ir ha-mishtale’aḥ – the goat sent off to Azazel as part of the Yom Kippur service – and the par ha’alem davar shel tzibbur – the sacrifice brought by the Sanhedrin when they mistakenly misled the people with an erroneous ruling, leading the community to sin. Rabbi Shimon adds another communal sin offering – the one brought when a mistaken ruling leads the community to commit an act of avoda zara.
Semikha as part of the sacrificial service in the Temple, was an important part of the process of atonement of the individual who brought the sin or guilt offering, as is indicated in the Torah (Vayikra 1:4). Semikha was performed as follows: The sacrificial animal is positioned in the northern part of the Temple courtyard with its head facing to the west. The person doing semikha places both of his hands on the head of the animal, between its horns. He then recites viduy, that is, he confesses the sins for which the sacrifice is being brought, as appropriate for a ḥatat, an asham or an ola (for neglecting positive commandments).
The semikha and viduy serve to clarify the connection between the person bringing the korban and the atonement that is sought by means of the sacrifice. In the cases of communal sacrifices where there was semikha, the kohen gadol acted as the representative of the community on Yom Kippur and three members of the Sanhedrin played that role when the par ha’alem davar shel tzibbur was brought.