Is it true that Zechariah 6:12-13 speaks of the Messiah as both a king and a priest? Let's find out in this interesting article.
The passage reads: "Behold a man whose name is the Shoot, who will spring up out of his place and build the Temple of the Lord. And he shall build the Temple of the Lord, and he shall bear glory. And he shall sit and rule on his throne, and the priest shall be on his throne. And a counsel of peace shall be between them [both]."
Some commentators identify the "man whose name is Shoot" as Zerubbabel others as the Messiah. "The Shoot" is called a ruler, not a king; and he is to build the Temple of the Lord. Moreover, the text does not speak of one individual but of two, the ruler and the (high) priest. Both individuals will interact harmoniously with each other, "And a counsel of peace shall be between them [both]." Thus, there is no truth to the suggestion that "the Shoot" combines the office of king and high priest.