The person with the measuring line (described in Zechariah 2:4 as a young man, i.e. Zerubbabel, cf. Esther 3:4; Esther 4:58) is evidently ascertaining the length of wall required. An angel bids the interpreting angel stop the measuring. A fortified wall is unnecessary, since the Lord will defend His own, and it would only check the expansion of Jerusalem.
Related Commentaries of Zechariah 2:1
Zechariah 2:1-5
1 I lifted up mine eyes again, and looked, and behold a man with a measuring line in his hand.
2 Then said I, Whither goest thou? And he said unto me, To measure Jerusalem, to see what is the breadth thereof, and what is the length thereof.
3 And, behold, the angel that talked with me went forth, and another angel went out to meet him,
4 And said unto him, Run, speak to this young man, saying, Jerusalem shall be inhabited as towns without walls for the multitude of men and cattle therein:
5 For I, saith the LORD, will be unto her a wall of fire round about, and will be the glory in the midst of her.