Albert Barnes Commentary Revelation 21:17

"And he measured the wall thereof, a hundred and forty and four cubits, [according to] the measure of a man, that is, of an angel." — Revelation 21:17 (ASV)

And he measured the wall thereof. In respect to its height. Of course, its length corresponded with the extent of the city.

An hundred and forty and four cubits. This would be, reckoning the cubit at eighteen inches, two hundred and sixteen feet. This is less than the height of the walls of Babylon, which Herodotus says were three hundred and fifty feet high. See Introduction to Isaiah 13:1.

As the walls of a city are designed to protect it from external enemies, the height mentioned here gives all proper ideas of security. We are to conceive of the city itself as towering immensely above the walls. Its glory, therefore, would not be obscured by the wall that was thrown around it for defense.

According to the measure of a man. The measure usually used by men. This seems to be added to prevent any mistake regarding the size of the city.

It is an angel who makes the measurement, and without this explanation, it might perhaps be supposed that he used some measure not commonly used by men, so that, after all, it would be impossible to form any definite idea of the size of the city.

That is, of the angel. That is, "which is the measure used by the angel." It was, indeed, an angel who measured the city, but the measure which he used was that in common use among men.