Jamieson, Fausset and Brown on Zechariah 3:2

2. the Lord--Jehovah, hereby identified with the "angel of the Lord (Jehovah)" (Zec 3:1).

rebuke thee--twice repeated to express the certainty of Satan's accusations and machinations against Jerusalem being frustrated. Instead of lengthened argument, Jehovah silences Satan by the one plea, namely, God's choice.

chosen Jerusalem--(Ro 9:16; 11:5). The conclusive answer. If the issue rested on Jerusalem's merit or demerit, condemnation must be the award; but Jehovah's "choice" (Joh 15:16) rebuts Satan's charge against Jerusalem (Zec 1:17; 2:12; Ro 8:33, 34, 37), represented by Joshua (compare in the great atonement, Le 16:6-20, &c.), not that she may continue in sin, but be freed from it (Zec 3:7).

brand plucked out of ... fire--(Am 4:11; 1Pe 4:18; Jude 23). Herein God implies that His acquittal of Jerusalem is not that He does not recognize her sin (Zec 3:3, 4, 9), but that having punished her people for it with a seventy years' captivity, He on the ground of His electing love has delivered her from the fiery ordeal; and when once He has begun a deliverance, as in this case, He will perfect it (Psa 89:30-35; Php 1:6).