This is the word of the Lord to Zerubbabel: “Not by might nor by power, but by my Spirit,' says the Lord Almighty. "What are you, O mighty mountain? Before Zerubbabel you will become level ground. Then he will bring out the capstone to shouts of ‘God bless it! God bless it (Zech 4:6-7)!’”

As it has been already pointed out, this section of chapter 4 of Zechariah was originally recorded as an independent oracle and placed right after 1:7, but later, it was moved from there and inserted in the present location by an editor (or the author himself). If it were still in the originally place, we would interpret this oracle simply as an oracle given to Zerubbabel and to Zechariah to encourage them as they faced the situation of that time, especially concerning the task of rebuilding the temple. However, since the oracle seemed to contain something much more—far beyond their current situation and into the distant future, it was moved into the middle of the vision that also deals with something of the future—especially, that of a drastic topographical change of Jerusalem.

The “mighty (great) mountain” was Mount Zion on which David’s palace once stood. It was still a high mountain, then, higher than any other parts of the city, but the oracle says, “Before Zerubbabel you will become level ground.” As “Joshua the high priest” in chapter 3 represented the nation of Israel as well as the city of Jerusalem that had been destroyed and burnt, “Zerubbabel” symbolically represented the kingdom that had come to exist under the Davidic covenant. As the horn of a nation is chopped off, the leveling of Mount Zion signifies the cutting off of the visible existence of David’s kingdom. The visible or physical boundary between Israel and the gentile nations would disappear, and the two would be united and amalgamated into one kingdom. In fact, the same thing has been revealed in the vision of a man with a measuring line in chapter two: “Jerusalem will be a city without walls (2:4).” Paul speaks of this amalgamation of Israel and Gentiles through Christ as follows:

For he himself is our peace, who has made the two one and has destroyed the barrier, the dividing wall of hostility, by abolishing in his flesh the law with its commandments and regulations. His purpose was to create in himself one new man out of the two, thus making peace, and in this one body to reconcile both of them to God through the cross, by which he put to death their hostility (Eph 2:14-16).

In other words, the former kingdom of Israel was overthrown and destroyed, and a new kingdom through Christ was established under the same Davidic covenant. And if the way a kingdom stands has changed, and a new kingdom has been built, then, the former foundation must have been removed, and a new foundation must have been laid.

Therefore, two different kinds of stones are mentioned in this oracle of Zech 4: “the capstone” that Zerubbabel will bring out, and “the plumb line” that he will come to have in his hand and people will rejoice at. Each of them is expressed as a “stone (eben)” modified by an unusual adjective that occurs only once and here in the Bible. The first one sounds like “the former stone,” and the second one “the stone of distinction”: the first one is to be carried out, and the second one is to be brought in.

Then the word of the Lord came to me: "The hands of Zerubbabel have laid the foundation of this temple; his hands will also complete it. Then you will know that the Lord Almighty has sent me to you. "Who despises the day of small things? Men will rejoice when they see the plumb line (the stone of distinction) in the hand of Zerubbabel (Zech 3:8-10).

“The former stone” was what was contained in the Ark of the Covenant, and “the stone of distinction” is “the living stone”—rejected by men but chosen by God and precious to him, and “God’s solid foundation” with an inscription saying, “The Lord knows who are his,” and “Everyone who confesses the name of the Lord must turn away from wickedness.”