Ezekiel 41:5-6

The wall enclosing the vestibule, holy place, and most holy place was six cubits (10 feet) thick. Rooms five cubits (8 feet 4 inches) deep surrounded this wall on all sides except the east. There were three stories of these rooms, 30 rooms on each level, for a total of 90 rooms. There was another wall on the outside of these rooms that bore their weight so the inner wall of the temple did not carry it. The purpose of these rooms was not revealed, but they may be for worship, fellowship, or storage.