Numbers 21:8

Make thee a fiery serpent, and set it upon a pole— The author of the Book of Wisdom sets this matter in its proper light, when he calls this fiery serpent a sign of salvation to put them in remembrance of God's laws; for he that turned himself towards it, says he, was not saved by the thing that he saw, but by thee, who art the Saviour of all. The healing virtue which accompanied the looking upon this image was derived from God alone, who was pleased in this manner to display his power, to make the Israelites sensible that these serpents were sent by him; and that this seemingly weak method of cure might convince them, that they had no reason to fear any evil whatsoever, provided they but made God their friend, whose power could procure so easy a remedy in all emergencies. To the same purpose our Saviour, in curing the man born blind, put clay upon his eyes, to shew that the cure was extraordinary and supernatural. Here all interpreters observe a remarkable similitude between the virtue of this brazen serpent erected on a pole, and that of Christ's death, and which is taken notice of by Christ himself. John 3:14. For, as no one could imagine that the bare sight of a serpent, imaged in brass, would cure the serpent's poison; to nothing is more true, however incredible it appeared at the time of the event, than that the only effectual means of propagating the Christian Religion, and of drawing all nations to the faith and obedience of the Gospel, and consequently of saving those who were sincere in that profession from the sting of death and the power of the devil, that old serpent, (Revelation 12:9; Revelation 20:2.) was the lifting up of Christ upon the cross, or putting him to death. This interpretation sufficiently removes all the objections of Voltaire, and such enemies of the Old Testament as pretend that Moses, by forming this brazen serpent, was himself an encourager of that idolatry which he so severely reprehends in others. There is no ground from the text to suppose that this brazen serpent was ever intended as an object of worship. The word which we render pole in this verse, signifies an ensign or banner; a sign erected with an intention that people may gather around it. Isaiah 5:26; Isaiah 49:22.

See commentary on Numbers 21:9