Zechariah 6:1

And I turned, and lifted up my eyes, and looked, and, behold, there came four (a) chariots out from between (b) two mountains; and the mountains [were] mountains of brass.

(a) By chariots here, as by horses before, he means the swift messengers of God to execute and declare his will.

(b) By the mountains he means the external counsel and providence of God, by which he has from before all eternity declared what will come to pass, and that which neither Satan nor all the world can alter.