Albert Barnes Commentary Ezekiel 40:38

"And a chamber with the door thereof was by the posts at the gates; there they washed the burnt-offering." — Ezekiel 40:38 (ASV)

The chambers—translate this as “and chambers, not yet described.” They were north of the altar, by the “posts” or pillars in front and along the sides of the gate-building. There were several gates in the gate-building.