“Joshua the high priest.” Joshua was the High Priest, as we see here and Haggai 1:14. “Joshua” and “Jeshua” are variant spellings of the same name, and it can be confusing to the English reader that Haggai and Zechariah use “Yehoshua” shortened to “Joshua” (cp. Haggai 1:14; 2:2, 4; Zech. 3:1), while Ezra and Nehemiah use “Jeshua” (cp. Ezra 3:2, 8; 5:2; Neh. 7:7). To make matters more confusing, since “Joshua” was a very common name, many people had that same name, so the reader has to be very careful about who is who.
In this context, “Joshua” the High Priest is not representing himself, but is a vision and Joshua the High Priest represents the spiritual side of Israel and Judah and their situation in the eyes of God. Sadly, Israel and Judah had been very sinful as nations. Joshua 3:8 says that Joshua and the other men who were with him were signs, they represented things, and Joshua represented the spiritual side of Israel. In the vision, God removes the filthy garments on Joshua (Zech. 3:4-5), and what that symbolizes is that God will remove the sin of Israel (cp. Zech. 3:9). God had used the image of filthy cloth to represent moral filth earlier in the Bible (cp. Isa. 64:6), and clothing is used that way here in Zechariah as well.
“Satan standing at his right hand to be an adversary to him.” This “Satan” is the Satan from Job 1, the Devil, the evil spirit who has been the constant adversary of God. This phrase is one of the times when transliterating the title “Satan” from the Hebrew text takes away some of the punch and meaning of the original text. Also, the Hebrew text actually reads, “the satan.” The word satan in Hebrew, Aramaic, and Greek means “adversary,” and a more literal translation of this phrase would be, “And he showed me Joshua…and the Adversary standing at his right hand to be an adversary to him.” Although translating the literal Hebrew “the Adversary” as “Satan” makes the English reading clearer to most readers, we are in danger of losing the fact that God is revealing to us that the Devil always acts out of his nature: one of his “names” is “the Adversary” and he always is and always will be an adversary to God.
Satan and his followers are evil and hurtful, and the wise Christian keeps a wary eye out for them. Satan’s followers carry out the works of Satan (John 8:44; Acts 13:10) and often come in sheep’s clothing and are disguised as servants of righteousness (Matt. 7:15; 2 Cor. 11:13-15). But if we keep our eye on the fruit they produce, we will know them (Matt. 7:16, 20).
Satan can be in the presence of the angel of Yahweh and Joshua the High Priest because God is a righteous God and in order to be that He has to allow Satan to accuse people if the situation warrants it. In this case it seems that Satan is present because he knows that Israel and Judah have not been obedient to God.
[For more on the names God gives to the Devil, see Appendix 14, “Names of the Devil”].