Charles Ellicott Commentary Ezekiel 43:12

"This is the law of the house: upon the top of the mountain the whole limit thereof round about shall be most holy. Behold, this is the law of the house." — Ezekiel 43:12 (ASV)

Upon the top of the mountain.— Compare to Ezekiel 40:2. The command to keep and observe everything is closed, as often in similar cases, by a summary statement of the reason: for the whole surroundings of the dwelling-place of the Most High are holy.

With Ezekiel 43:13 a new part of the vision begins, extending to Ezekiel 46:24, describing the new ordinances of the sanctuary. This is fitly opened with a description of the altar for the sacrifices, the central act of the ancient worship.