Leviticus 16:11

'וכפר בעדו וגו‎ AND HE SHALL MAKE AN EXPIATION FOR HIMSELF etc. — This implies a second confession of sins which he was to make for himself and on behalf of his brother-priests, who may all be termed “his house”, as it said (Psalms 135:19) “Bless the Lord, o house of Aaron, etc." (cf. Shevuot 14a). Hence we learn that the priests become atoned for by means of it (the bullock). The expiation effected by it extended, however, only to those sins committed by causing uncleanness to the Sanctuary or holy things (i.e. by the priests having entered the Sanctuary or eaten of the holy things in such a state), as it is said (v. 16) “And he shall make an expiation for the holy place because of the uncleanness [of the children of Israel] etc.”.

וְהִקְרִ֨יב אַהֲרֹ֜ן אֶת־פַּ֤ר הַֽחַטָּאת֙ אֲשֶׁר־ל֔וֹ וְכִפֶּ֥ר בַּֽעֲד֖וֹ וּבְעַ֣ד בֵּית֑וֹ וְשָׁחַ֛ט אֶת־פַּ֥ר הַֽחַטָּ֖את אֲשֶׁר־לֽוֹ׃

And Aharon shall bring the bullock of the sin offering, which is for himself, and shall make atonement for himself, and for his house, and shall kill the bullock of the sin offering which is for himself: