Matthew Poole and continuators on Revelation 21:16

16 And the city lieth foursquare, and the length is as large as the breadth, And he measured the city with the reed, twelve thousand furlongs. The length, and the breadth and the heighth of it are equal .

The Church Militant, measured by the Reed of the Word, is equal in its parts. Some parts of it are purer than others; but in the New Ierusalem all parts shall be equal in perfection and purity, as all the sides of a thing foursquare are equal.