The fiery serpent in the wilderness was a shadow of what Jesus would accomplish on the cross:
And the LORD said unto Moses, Make thee a fiery serpent, and set it upon a pole: and it shall come to pass, that every one that is bitten, when he looks upon it, shall live. And Moses made a serpent of brass, and put it upon a pole, and it came to pass, that if a serpent had bitten any man, when he beheld the serpent of brass, he lived (Numbers 21:8-9).
And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up (John 3:14).
It is staggering to think of Jesus being compared to a serpent, but the truth of the matter is that He actually became a curse for us (Galatians 3:13) on the cross. The pure and holy one, the spotless Lamb of God, the one who knew no sin, was made to be sin for us (2Cor.5:21)! He became as that serpent, so that we might live.
The curse that He bore included our sicknesses as well as our sins. Thus Jesus referred back to the serpent on the pole.
In that instance, God cancelled out the punishment for the recent sin of the Israelites. Those who looked upon the serpent were also healed. But they had to look. They had to see their tormentor stifled and lifted out of the way on a pole.
In the same way, we have to look and behold our sin and sickness taken out of the way and nailed to the cross. Just as forgiveness is based only on what Jesus did, healing is as well. We didn’t do anything to earn forgiveness, but we had to look to Jesus to receive it. In the same way, we can’t do anything to earn healing. But we have to look to Jesus. He earned it on our behalf: he was wounded for our transgressions, he was bruised for our iniquities: the chastisement of our peace was upon him; and with his stripes we are healed (Isaiah 53:5).
God does not will His children to be sick, any more than you or I would will our children to be sick. It’s time to take a stand against the devil’s works. By embracing sickness, the church has marginalized the great purchase Jesus made for us with His blood. If God healed those sinners in Moses’ time, under the old covenant, how much more should we expect Him to do the same for us in the new covenant, which is the better and greater covenant!