Numbers 21:9

Moses made a serpent of brass— That it might resemble a serpent of a flaming colour; and, being splendid, might be seen far and near. Naturalists observe, that the sight of the image of the creature by which men were bitten, tended of itself rather to increase disease, and fill them with greater anguish, by disturbing their imagination: if so, it was the more proper to convince the Israelites that their cure came from God alone, who made that, of which the aspect was naturally hurtful, to be the means of their recovery. Those who would see more upon this subject may consult Scheuchner on the place. Mr. Saurin observes, that the Jews have a remarkable saying, "that as the bitings of the fiery serpents were cured by the Israelites looking up to the brazen serpent; so will be the bitings of the old serpent inflicted on Adam and his posterity at the time of the Messiah." If this saying (says he) were known in the days of our Saviour, it is probable that he alluded to it, when he said to Nicodemus, as Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up, that whoever believeth in Him should not perish, but have eternal life. John 3:14.

It is plain, that our Lord compares faith to the look which the Israelites, being wounded, by the bitings of the fiery serpents, cast upon that of brass. He also compares the healings which attended their look to the fruits of faith, and the lifting up of the serpent to his exaltation upon the cross. This allusion is so much the more happy, as, according to the observation of some critics, the Syriac word which our Lord used signifies both to lift up and to crucify. He used this word in the same sense, when he said, and I, if I be lifted up from the earth, will draw all men unto me; John 12:32. The prophets made the same allusions too, perhaps, when, speaking of the evangelical ages, they said, at that day shall a man look to his Maker, and his eyes shall have respect to the Holy One of Israel; Isaiah 17:7 and, in another place, they introduce the Saviour saying, look unto me, and be saved, all the ends of the earth; for I am God, and there is none else. Isaiah 45:22. See Saurin, Diss. 63.