John Calvin's Bible Commentary
Zechariah 6:15
The Prophet also states, that men would come from remote lands to contribute labor or wealth towards the building of the temple; for the word building may refer to either of these two things. Come then shall those from far. Before this time gifts had been presented by Gentile nations, but the temple was not built but by Solomon and his people. God then promises here something more, and that is, that helpers would assist in building the temple, who had been till then wholly aliens. It is indeed certain, that in the age of Zechariah contributions had been made by Cyrus; but the Prophet refers to nothing of this kind: he promises something more. It hence follows that this prophecy must necessarily be referred to the promulgation of the gospel; for then it was that strangers began to contribute their labor and their wealth towards building a temple to God. Though then Cyrus gave a large sum of money towards the erection of the temple, yet the allusion here is not to his liberality. And after Cyrus no stranger had been so liberal: for Herod, who raised up a great and a very splendid building, was not from far; nay, he wished to be thought one of the people. We then see that this prophecy cannot be otherwise referred than to the building of the spiritual temple, when Gentiles, formerly remote from God’s people, joined them as friends, and brought their labor to the work of building the temple, not with stones or wood, or with other corruptible materials, but with the doctrine and the gifts of the Holy Spirit.
He then adds, ye shall know that Jehovah of hosts has sent me to you. Of this kind of knowledge we have spoken elsewhere. It indeed behaved the Jews from the first to feel assured respecting the truth of this prophecy; but when the effect or experience itself was added, they then began to know more clearly. It is then the same as thought the Prophet had said, “God, who speaks by my mouth, will not disappoint you, as he will at length accomplish what I now declare; and experience itself will be a witness that I have been a true and faithful Prophet.” And he calls Him the God of hosts, that the Jews, hearing that what he had said proceeded from Him whose power is infinite, might be confirmed in their faith. There was then no reason for them to doubt as to the accomplishment, for there is nothing that can resist God, when it pleases him to unfold his power.
It follows, If by hearing ye will hear the voice of Jehovah your God. Zechariah promises to the Jews here conditionally — if they became obedient to God, and continued in obedience to his word and in his doctrine; for unbelief deprives men of all participation in God’s favor. It is indeed true that had all become unbelieving, Christ would have come; for God as he is true would not change his purpose were the whole world to become false. Since then the faithfulness of God depends not on men, we ought not so to take what the Prophet says here, If ye will hear the voice of Jehovah, as though they could, by being unfaithful to God, have rendered void the accomplishment of this prophecy. Their defection, then, yea, that of the whole nation, could not have prevented Christ from coming forth in his own appointed time. But the Prophet had another thing in view, even this — that the Jews would become partakers of this blessing, or would enjoy, so to speak, this favor, if they embraced God’s promise, and obediently submitted to his law. For though Christ has already come as the Redeemer of the world, yet we know that this benefit is not come to all, and why? Because many through unbelief close the door against God and his grace through Christ. Hence the faithful alone really know that God has spoken, and really partake of his favor, and for this reason, because they hear his voice; that is, they first by faith receive what God offers, and then they fall not away from his truth, but continue in the obedience of faith to the end.
What the Prophet then had in view, was to show to the Jews that those things were spoken in vain, as to them, if they did not attend to God. And he shows the way in which they were to be attentive, even by hearing the voice of God, that is, by renouncing their own thoughts, and by not esteeming God untrue, though he promised what seemed incredible. If then they denied themselves, banished their own imaginations, wholly attended to God’s word, and believed what he had said as a Prophet, he assures them that they would really find that which he taught them to be true to their own salvation, even this — that Christ would come to be a king and a priest, to secure perfect happiness to his people.