James refers to someone who is incapacitated physically. Thus oil can represent both the medical & the spiritual spheres of life. Jesus Christ is Lord over both the body & the spirit.
The elders should be on call to respond to the illness of any members & the church should stay alert to pray for the needs of all its members.
"And the prayer of faith," does not refer to the faith of the sick person, but to the faith of the church. God heals, faith doesn't, & all prayers are subject to God's will. That is why God often waits for our prayers of faith before intervening to heal a person.
"Confess your faults" can be translated "Confess your sins." Christ has made it possible for us to go directly to God for forgiveness, but confessing our sins to one another still has an important place in the life of the church. In Christ's Kingdom, every believer is a priest to other believers. We must help others come to Christ & tell them of Christ's forgiveness.
The Christian's most powerful resource is communion with God through prayer. Since God's power is infinitely greater than our own, it only makes sense to rely on it - especially because he encourages us to do so.
For more about the great prophet Elijah (Elias), read his Profile in I Kings 18.
Clearly the person who has slipped away is a believer who has fallen into sin - one who is no longer living a life consistent with his belief. Christians disagree over whether or not it is possible for people to lose their salvation, but all agree that those who move away from their faith are in serious trouble & need to repent. James urges Christians to help backsliders return to God. By taking the initiative, praying for the person, & acting in love, we can meet the person where he is & bring him back to God.
The book of James emphasizes faith in action. Right living is the evidence of result of faith. The church must serve with compassion, speak lovingly & truthfully, live in obedient to God's commands, & love one another. The body of believers ought to be an example of heaven on earth, drawing people to Christ through love for God & one another. If we truly believe God's Word, we will live it day by day. God's Word is not merely something we read or think about, but something we do. Belief, faith & trust must have hands & feet - ours!
Reference summary used from the Life Application Bible KJV, Tyndale House Publishers, Inc., Wheaton, Illinois