I. In the words "for sin and for uncleanness" there is apparently an allusion in the former to the water used in the purification of the Levites at their consecration, and in the latter to the water for the purifying of the congregation of Israel, prepared from mixing the ashes of the red heifer slain as a sacrifice with water. As water applied to the person removes bodily defilement, it becomes a fitting emblem of that which removes from the inner man moral defilement. Here the reference is to the cleansing energy which He who pours on men the spirit of grace and supplication bestows on all who truly repent, and which comes to men through the sacrificial death of Christ, whose "blood cleanseth from all sin."
II. The fountain opened, its cleansing waters are free to all to the inhabitants of Jerusalem as well as the house of David. The grace of salvation is free to all without respect of persons.
III. True repentance will show itself on the part of those who are subjects of it, in the relinquishment of all former objects of evil attachment, and the entering upon a new life of godliness and holy service. So should it be with the covenant people after the great mourning and the attendant cleansing. As the sins to which Israel was most prone, and which brought on the nation the Divine judgments, were idolatry and false prophecy, so the restoration of the people to a new life of godliness and righteousness is depicted by the extermination of idols and false prophets from the land.
IV. It is for the house of David and the inhabitants of Jerusalem that this fountain is said to be opened. They seem to err grievously, however, who infer from this that the prophecy refers to the final conversion of the Jewish people. The prophets are wont to describe the new dispensation in language borrowed from the conditions and usages of the old; and we interpret them aright when keeping this in view; we understand their descriptions not as representations of simple historical facts, but as serving as the copy and shadow of the heavenly things, and as finding their fulfilment in crises and conditions of the kingdom of heaven on earth. They go upon the presumption that the Israel of God was never to be abolished, that its continuity was never to be interrupted, that though the outward national Israel might be cast off because of their rejection of the Good Shepherd, the true Israel, the reality of which the other was but the symbol, the Israel that was really Israel, should continue for ever.
W. Lindsay Alexander, Zechariah's Visions and Warnings,p. 271; see also Homiletic Magazine,vol. x., p. 353.
Reference: R. C. Anderson, Christian World Pulpit,vol. xxxii., p. 53.