Commentary for Zechariah 12:5

And the princes of Judah shall say to themselves when they see that the others who were gathered are plagued with this plague, and they are saved.

The "chiefs of Judah" are the high officers and the second-in-commanders of the nation, they shall see God's hand upon their enemies and that they are saved from it. Because of this, they will say in their hearts that this is the finger of God, and they will beseech the inhabitants of Jerusalem that they pray and cry out to their God, for even while Jerusalem lies in waste, God still watches over it, and prayers done there are accepted by Heaven, and thats what "God, the lord of hosts, command for me by Jerusalem of their God". This means that every person in a position of honor in all of the cities of Judah will say "command for me and thus encourage the inhabitants of Jerusalem to pray on my behalf"

The inhabitants of Jerusalem were my strength, etc. The inhabitants of Jerusalem, who know that we came upon them against our will, strengthened my help with their prayer by the Lord, their God.