Christians can and do get sick, they get injured, they lose body parts or the function of them. Some are born with genetic or developmental defects or had disease passed on to them in utero. In light of what Christ has done for us, why? We have already touched on the general principle: the dying bodies we were born with are susceptible to such things. So what should a Christian do about sickness?"
My response is that they should call upon God. Call upon God, I must be joking, right? No, that is the biblical answer! There are so many things God does for us without us consciously asking (we all breathe air at his discretion, without asking), but there are others that take the word of our mouth expressing the faith of our hearts to get. Our natural bodies do combat sickness and recover from or adapt to its effects, Christian or not. So it certainly is possible to be healed without asking (i.e. coming to him to receive), but when sickness crosses a certain threshold, I would say that is the exception rather than the rule.
I think the example of Jesus is illuminating here: everyone who came to him, or was brought to him to seek healing from him was healed by him. Have you ever wondered what happened to the sick that heard about Jesus, but didn't bother to come themselves or had no one bring them? What happened to those that did not have faith that compelled them to come and receive? I know it's a supposition, but I'd say they stayed sick, even died that way.
The Bible says flatly, if you're sick it's time to pray, and specifically, to get the church to use it's power of agreement in prayer for you. So whether you look at the pattern of folk getting healed in the gospels, or you hear the teaching of James on the subject, the bottom line is the same: when those in the community of faith get sick, they must ask God for healing! Healing is provided in the atonement, but like the atonement itself, it is not applied to humans generally apart from a receiving faith communicated to God.
As far as we know, the only time the Apostles, in doing Jesus' bidding in the gospels, were stifled was when there was a lack of faith. I hate the expression, "faith healing," but there is a measure of truth in it. When we come and ask Jesus for anything, it will be unto us according to our faith. A double-minded man will receive nothing from the Lord, even though Jesus died to provide it.
When we come to God for healing, we must come boldly, believing he hears us, and realizing that those stripes laid upon the back of Jesus were laid there for our healing. It is God's determined will to act on our behalf and heal us: "by his stripes we are healed!" So when we call upon the elders to pray over us, we cannot merely hope that it will work, we must know in our heart that it will.
But honestly, how can anyone know that? Well, all true Christians know that forgiveness of sins was an outcome of Jesus' atonement. They have no trouble knowing what to do when conviction of sin and a guilty conscience strike them. They go to God, confess their sin, and appropriate the forgiveness won at the cross. Most Christians have little difficulty believing that God forgives them when they ask him to do so.
After all, they have the pattern of the Lord's prayer, they have the historical fact of the passion, and they have the specific teaching of an Apostle. When they ask God to forgive them, they do so with confidence and the burden lifts. Why should they approach healing any differently? We have the pattern of God's management of his flock, we have the historical fact of the passion (specifically, those stripes), and we have the clear teaching of an apostle.
So when we ask God to heal us, we should do so with the same confidence we have that he will forgive us. They are part and parcel of the same thing. But wait a minute, there are believing folk that remain in illness or disability, what about them? We'll tackle that in the next post on the subject.