zechariah 6:15 And they that are far off shall come and build in the temple of the LORD, and ye shall know that the LORD of hosts hath sent me unto you. And this shall come to pass, if ye will diligently obey the voice of the LORD your God. - Free Bible Online

      15. they . . . far off shall . . . build--The reason why the crowns were made of gold received from afar, namely, from the Jews of Babylon, was to typify the conversion of the Gentiles to Messiah, King of Israel. This, too, was included in the "peace" spoken of in Zec 6:13 (Ac 2:39; Eph 2:12-17). Primarily, however, the return of the dispersed Israelites "from afar" (Isa 60:9) to the king of the Jews at Jerusalem is intended, to be followed, secondly, by the conversion of the Gentiles from "far off" (Zec 2:11; 8:2-2, 23; Isa 60:10; 57:19).
      build in the temple--Christ "builds the temple" (Zec 6:12, 13; Heb 3:3, 4): His people "build in the temple." Compare Heb 3:2, "Moses in His house."
      ye shall know, &c.--when the event corresponds to the prediction (Zec 2:9; 4:9).
      this shall come to pass, if ye . . . obey, &c.--To the Jews of Zechariah's day a stimulus is given to diligent prosecution of the temple building, the work which it was meanwhile their duty to fulfil, relying on the hope of the Messiah afterwards to glorify it. The completion of the temple shall "come to pass," if ye diligently on your part "obey the Lord." It is not meant that their unbelief could set aside God's gracious purpose as to Messiah's coming. But there is, secondarily, meant, that Messiah's glory as priest-king of Israel shall not be manifested to the Jews till they turn to Him with obedient penitence. They meanwhile are cast away "branches" until they be grafted in again on the Branch and their own olive tree (Zec 3:8; 12:10-12; Mt 23:39; Ro 11:16-24).

JFB.