Reference for Horayot 2:1

הוֹרָה כֹהֵן מָשִׁיחַ לְעַצְמוֹ, שׁוֹגֵג וְעָשָׂה שׁוֹגֵג, מֵבִיא פָר. שׁוֹגֵג וְעָשָׂה מֵזִיד, מֵזִיד וְעָשָׂה שׁוֹגֵג, פָּטוּר, שֶׁהוֹרָאַת כֹּהֵן מָשִׁיחַ לְעַצְמוֹ, כְהוֹרָאַת בֵּית דִּין לַצִּבּוּר:

If the anointed priest [i.e., If the high-priest, anointed with the anointing oil] unwittingly ruled for himself [that something was permitted] and transgressed [by himself] unwittingly [in a thing deliberate transgression of which is liable to kareth], he brings a bullock. (If he ruled) unwittingly and transgressed wittingly, or (ruled) wittingly and transgressed unwittingly, he is exempt. For the ruling of the anointed priest for himself is like the ruling of beth-din for the congregation.

Jastrow