Jamieson, Fausset and Brown on Ezekiel 41:9

9. that which was left--There was an unoccupied place within chambers that belonged to the house. The buildings in this unoccupied place, west of the temple, and so much resembling it in size, imply that no place was to be left which was to be held, as of old, not sacred. Manasseh (2Ki 23:11) had abused these "suburbs of the temple" to keeping horses sacred to the sun. All excuse for such abominations was henceforth to be taken away, the Lord claiming every space, and filling up this also with sacred erections [Fairbairn].