Albert Barnes Commentary Ezekiel 45:2

"Of this there shall be for the holy place five hundred [in length] by five hundred [in breadth], square round about; and fifty cubits for the suburbs thereof round about." — Ezekiel 45:2 (ASV)

The “sanctuary” here probably means the whole temple precincts.

Suburbs—literally, as noted in the margin. To mark out more distinctly the sacred precincts, a vacant space of fifty cubits was left on all sides.