Albert Barnes Commentary Zechariah 2:1

"And I lifted up mine eyes, and saw, and, behold, a man with a measuring line in his hand." — Zechariah 2:1 (ASV)

A man with a measuring line in his hand — This is probably the Angel of the Lord, of whom Ezekiel has a similar vision.

Jerome states: “He who before, when he lifted up his eyes, had seen in the four horns mournful things, now again lifts up his eyes to see a man, of whom it is written, Behold a man whose name is the Branch (Zechariah 6:12); of whom we read above, Behold a man riding upon a red horse, and he stood among the myrtle trees, which were in the bottom (Zechariah 1:8). Of whom also the Father says, He built My city, whose builder and maker is God (Hebrews 11:10).”

He too is seen by Ezekiel in a description like this: a man whose appearance was like the appearance of brass (Ezekiel 40:3), that is, burnished and shining as fire, with a line of flax in his hand and a measuring reed (Ezekiel 1:7). The office also seems to be one of authority, not to measure the actual length and breadth of Jerusalem, but to lay down what it should be. Cyril says this is “to mark it out broad and very long.”