Zechariah was the Prophet of the returning exiles, and his great work was to hearten them for their difficult task, with their small resources and their many foes, and to insist that the prime condition to success, on the part of that portion of the nation that had returned, was holiness. So his visions, of which there is a whole series, are very largely concerned with the building of the Temple and of the city. In this one, he sees a man with a measuring-rod in his hand coming forth to take the dimensions of the still un-existing city of God. The words that I have read are the centre portion of that vision. You notice that there are three clauses, and that the first in order is the consequence of the other two. 'Jerusalem shall be builded as a city without walls ... for I will be a wall of fire round about her, and the glory in the midst of her.' And that exuberant promise was spoken about the Jerusalem over which Christ wept when he foresaw its inevitable destruction. When the Romans had cast a torch into the Temple, and the streets of the city were running with blood, what had become of Zechariah's dream of a wall of fire round about her? Then can the divine fire be quenched? Yes. And who quenched it? Not the Romans, but the people that lived within that flaming rampart. The apparent failure of the promise carries the lesson for churches and individuals to-day, that in spite of such glowing predictions, there may again sound the voice that the legend says was heard within the Temple, on the night before Jerusalem fell. 'Let us depart,' and there was a rustling of unseen wings, and on the morrow the legionaries were in the shrine. 'If God spared not the natural branches, take heed lest He also spare not thee.' Now let us look, in the simplest possible way, at these three clauses, and the promises that are in them; keeping in mind that, like all the divine promises, they are conditional. The first is this:-- I. 'I will be a wall of fire round about her.'