Ezekiel 40:45-46

45He [who was guiding me] said to me, “This is the chamber which faces toward the south; it is for the priests who have the responsibility and take care of the temple;

46but the chamber which faces toward the north is for the priests who have the responsibility and take care of the altar. These are the sons of Zadok, who [alone] from the sons of Levi come near to the Lord to minister to Him.”