Matthew Poole and continuators on Ezekiel 40:38

38 And the chambers and the entries thereof were by the posts of the gates , where they washed the burnt-offering.

Either the six, three on one side, and three on the other, as before in the Gates of the outer Court, or else Chambers built on purpose for the uses here specified, as some conjecture.

The doors, as well as the Chambers, were by the Pillars probably adjoining to them.

Though some have thought, the North Gate was that alone, where they washt the Burnt offering, yet others conceive 'twas done at the East Gate too, if not at the South also, and the plural number warrants us to look for an other Gate, beside the North, when 'tis said, these chambers were by the Posts of the Gates, Plural.

God commanded, that the legs and entrails of this burnt offering should be washed, Lev. 1.13. now here they did that, and whether these chambers were built for this use onely, or put to this, as to other holy uses, is not greatly material to enquire.