"4 From Mount Hor they set out by the way to the Red Sea, to go around the land of Edom. And the people became impatient on the way. 5 And the people spoke against God and against Moses, “Why have you brought us up out of Egypt to die in the wilderness? For there is no food and no water, and we loathe this worthless food.” 6 Then the Lord sent fiery serpents among the people, and they bit the people, so that many people of Israel died. 7 And the people came to Moses and said, “We have sinned, for we have spoken against the Lord and against you. Pray to the Lord, that he take away the serpents from us.” So Moses prayed for the people. 8 And the Lord said to Moses, “Make a fiery serpent and set it on a pole, and everyone who is bitten, when he sees it, shall live.” 9 So Moses made a bronze serpent and set it on a pole. And if a serpent bit anyone, he would look at the bronze serpent and live."
Numbers 21:4-9
The provision God made for Israel illustrates the great gospel provision for sin. What is the significance of the uplifted serpent of brass? Matthew Henry says, 'That which cured was shaped in the likeness of that which wounded'. This is the key. Brass speaks of sin judged (cf the brazen altar in the Tabernacle, where the burnt offering for sin was sacrificed). Thus, here for Israel was the symbol, of substitutionary atonement their sin, represented by the serpent, was cursed and cancelled, and it was this they were bidden to look upon. Judgment cannot come where judgment has already been. So Christ, for our sakes, and for our healing, was made in the likeness of sinful flesh: He was made sin for us, on the bitter cross, and was lifted up from the earth, when He bore in His own body the judgment of a holy God upon sin. What is important for us to see is the identification of the Saviour with the sin, in both cases. From our point of view, what this says to us is that our sin must go to the cross to be judged and cancelled out, and that it did go to the cross, on the spotless shoulders of the Lamb of God. And it is because it was, once for all, dealt with and done away, that there is hope, and healing, and forgiveness for the children of men. As the old hymn puts it, 'There is life for a look at the Crucified One'.