John Calvin Commentary Zechariah 12:5

"And the chieftains of Judah shall say in their heart, The inhabitants of Jerusalem are my strength in Jehovah of hosts their God." — Zechariah 12:5 (ASV)

He still continues the same subject — that however small and feeble the flock of God might be, it would still have sufficient strength, for the Lord would stand on the side of those who fled to Him. Though Jerusalem was not yet filled with citizens, and though there was only one city, Zechariah still testifies that its strength would be invincible; but he speaks of the chiefs of Judah comparatively.

Previously, we know, it had a great number of men, and great armies were raised from that one tribe and the half-tribe of Benjamin. Though there were previously many provinces, and though the country was full of populous towns, Jerusalem alone had at that time almost begun to be inhabited; but the Prophet says here that though the whole Church was gathered within the narrow confines of one city, it would still have sufficient strength to resist all the attacks of enemies.

Then the chiefs of Judah shall say; that is, though previously the governors or commanders of thousands had forces in their various towns, now all would look to one city, for the land was nearly deserted and without inhabitants. At the same time, they were to maintain hope, because their strength was to be in the Lord.

Some insert a conjunction, “Strength will be to me and to the citizens of Jerusalem,” but they distort the meaning. For the Prophet meant to say in one sentence what I have stated: that the eyes of all would be directed to one city only, and that there would still be sufficient ground for hope and confidence, because they would become strong, not in themselves, but in their God.

There is a change of number when he says, “a strength to me,” for he had spoken of chiefs; it ought then to have been lanu, “to us.” But he now introduces each of them as speaking, as though each had said, “No one of the chiefs shall look to his own land, but, on the contrary, shall direct his eyes to the holy city and be content with the defense of a few men.”

Therefore, he says, In Jehovah of hosts, their God; for He means that God would then be the protector of that people whom He had for a time forsaken. And he calls Him again Jehovah of hosts in order to display His invincible power, lest the minds of the godly should fail through fear when they see themselves far unequal to their enemies.