Charles Ellicott Commentary Ezekiel 42:20

"He measured it on the four sides: it had a wall round about, the length five hundred, and the breadth five hundred, to make a separation between that which was holy and that which was common." — Ezekiel 42:20 (ASV)

It had a wall. —Around this vast enclosure on all sides was a wall, not of the slight character like that in Ezekiel 42:7; but the same word is used as in Ezekiel 40:5, of the massive wall surrounding the outer court. The object of this enclosure was to protect the sanctity of the Temple and its courts, to make a separation between the sanctuary and the profane place.