The scriptural basis for faith healing cited by its advocates is Isaiah 53:4:
Surely our griefs He Himself bore, And our sorrows He carried; Yet we ourselves esteemed Him stricken, Smitten of God, and afflicted.
It's called the doctrine of Healing in the Atonement. That is, Jesus died not only for our sins on the cross, but also our sicknesses. And the same faith that saves us can also heal us.
the KJV rendering does not appear to support that view. However, other translations do seem to.
NIV:
Surely he took up our infirmities and carried our sorrows, yet we considered him stricken by God, smitten by him, and afflicted.
And Matthew, led by the Spirit, rendered Isaiah 53:4 as follows:
Matthew 8:17 KJV:
Himself took our infirmities and bare our sicknesses.
So, the matter is settled right? Well, not quite.
Let's look at the context surrounding Matthew's rendering. Here are verses 16-17
When the even was come, they brought unto him many that were possessed with devils, and he cast our the spirit with his word, and healed all that were sick. 17 That it might be fulfilled which was spoken by isaiah the prophet, saying, Himself took our infirmities, and bare our sicknesses.
This passage tells us that Isaiah 53:4 was fulfilled in the evening, in Capernaum (8:5). A specific time and place. Jesus was alive.
So, Matthew, led by the Spirit, applied Isaiah 53:4 as being fulfilled in Jesus' life, not his death.
Thus falls the doctrine of Healing in the Atonement.
Another flaw: If healing is in the atonement, then all that is required is the faith of the sick person--no faith healers required.
And still another: If one has the gift of healing, the faith of the sick person is not required. The healer cannot ever fail.
I've wondered why those who claim to have the healing gift don't clean out the hospitals.
Now, I believe in divine healing. I believe that God sometimes heals in response to prayer (but not always).