Ezekiel 40:38

Then he brought me into the outer court, and behold, there were chambers and a pavement made for the court all around; thirty chambers faced the pavement.

From the outside to the inner gate were chambers for the singers in the inner court, one of which was at the side of the north gate, with its front toward the south, and one at the side of the south gate facing toward the north.

Then he said to me, “This is the chamber which faces toward the south, intended for the priests who keep the responsibility of the house;

but the chamber which faces toward the north is for the priests who keep the responsibility of the altar. These are the sons of Zadok, who from the sons of Levi come near to Yahweh to minister to Him.”

Then a measuring rod like a staff was given to me, saying, “Get up and measure the sanctuary of God and the altar, and those who worship in it.