First, the true source of strength and success, as shown by the vision, is declared in plain terms. What fed the lamp? Oil, which symbolises the gift of a divine Spirit, if not in the full personal sense as in the New Testament, yet certainly as a God-breathed influence, preparing prophets, priests, kings, and even artificers, for their several forms of service. Whence came the oil? From the two olive-trees, which though, as verse 14 shows, they represented the two leaders, yet set forth the truth that their power for their work was from God; for the Bible knows nothing of 'nature' as a substitute for or antithesis to God, and the growth of the olive and its yield of oil is His doing. This, then, was the message for Zerubbabel and his people, that God would give such gifts as they needed, in order that the light which He Himself had kindled should not be quenched. If the lamp was fed with oil, it would burn, and there would be a Temple for it to stand in. If we try to imagine the feebleness of the handful of discouraged men, and the ring of enemies round them, we may feel the sweetness of the promise which bade them not despond because they had little of what the world calls might. We all need the lesson; for the blustering world is apt to make us forget the true source of all real strength for holy service or for noble living. The world's power at its mightiest is weak, and the Church's true power, at her feeblest, is omnipotent, if only she grasps the strength which is hers, and takes the Spirit which is given. The eternal antithesis of man's weakness at his haughtiest, and God's strength even in its feeblest possessors, is taught by that lamp flaming, whatever envious hands or howling storms might seek to quench it, because fed by oil from on high. Let us keep to God's strength, and not corrupt His oil with mixtures of foul-smelling stuff of our own compounding. Next, in the strength of that revelation of the source of might a defiant challenge is blown to the foe. The 'great mountain' is primarily the frowning difficulties which lifted themselves against Zerubbabel's enterprise, and more widely the whole mass of worldly opposition encountered by God's servants in every age. It seems to bar all advance; but an unseen Hand crushes it down, and flattens it out into a level, on which progress is easy. The Hebrew gives the suddenness and completeness of the transformation with great force; for the whole clause, 'Thou shalt become a plain,' is one word in the original.