Zechariah 3:1

Zechariah’s guiding angel next showed the prophet, in his vision, Joshua (lit. Yahweh saves), Israel’s current high priest (Zechariah 6:11; Ezra 5:2; Nehemiah 7:7; Haggai 1:1), standing before the angel of the Lord (Zechariah 1:11-12). "The accuser" (lit. "the Satan," Heb. hasatan) was standing at Joshua’s right hand prepared to accuse him before the angel of the Lord (cf. Job 1:6-12; Job 2:1-7; Revelation 12:10). The writer made a play on the Hebrew word in its noun and verb forms here translated "Satan" and "accuse." [Note: See Sydney H. T. Page, "Satan: God’s Servant," Journal of the Evangelical Theological Society 50:3 (September 2007):449-65.] Standing at the right hand was the traditional place were an accuser stood in Jewish life (cf. 1 Chronicles 21:1; Psalms 109:6).

"The term satan, when used without the definite article, usually refers to a human adversary. The one exception is in Numbers 22:22; Numbers 22:32, where the angel of the Lord assumes the role of Balaam’s adversary. In 1 Chronicles 21:1, the term probably refers to a nearby nation, though some prefer to take the word in this context as a proper name, ’Satan.’ When the term appears with the article, as it does here and in Job 1-2, it is a title for a being who seems to serve as a prosecuting attorney in the heavenly court." [Note: Robert B. Chisholm Jr., Handbook on the Prophets, p. 460.]

". . . sin exposes the sinner to satanic attack not only in the case of unbelievers (Matthew 12:43-45), but believers as well (1 Corinthians 5:5; 1 John 5:16)." [Note: Unger, p. 57.]

Evidently the scene that Zechariah saw took place in the temple.

"The first three visions brought the prophet from a valley outside the city to a vantage-point from which the dimensions of the original Jerusalem could be seen. In the fourth and fifth visions he is in the Temple courts, where the high priest officiated and had access to God’s presence." [Note: Baldwin, pp. 112-13.]

"Joshua is standing in a tribunal, where he is being accused of unfitness for the priestly ministry." [Note: Merrill, p. 131.]

Another view is that he was not on trial but simply ministering to the Lord.