The “sanctuary” here probably means the whole temple precincts.
Suburbs - literally, as margin. To mark out more distinctly the sacred precincts, a vacant space of fifty cubits was left on all sides.
Related Commentaries of Ezekiel 45:2
Ezekiel 45:2
2 Of this there shall be for the sanctuary five hundred in length, with five hundred in breadth, square round about; and fifty cubits round about for the suburbsa thereof.