Today's verse is Mark 6:13: "And they cast out many demons and anointed with oil many who were sick and healed them." A part of the Twelve's ministry, as they were sent out by Jesus, was the anointing of oil for the sick. Why do this? In that day, oil was a medicinal substance. It had healing properties. Moreover, oil throughout the Bible represents the Holy Spirit. So when the Twelve anointed with oil, they were claiming the power of the Holy Spirit over those possessed by demons and the sick.
In James 5:13-14, a similar adjuration is given by James to the church. If anyone is sick, they are to call for the elders of the church. The elders will then anoint with oil, lay hands on the sick and pray for healing. These verses say that the prayers of faith will then lift up the one who is sick.
If oil is symbolic of the Holy Spirit, then it's the Holy Spirit who has authority over the demonic and illness. The prayer of faith simply empowers the Holy Spirit to do what he does: the will of God.
If you are sick today, and you are a member of a Body of Christ, you may want to call for the elders of the church to lay hands on you, anoint you with oil and pray for you to be healed. Only God is the healer. He alone decides who will be healed. But when elders anoint with oil, lay hands on and pray in faith for God to heal, coupled with our faith, there is a powerful presence of the Holy Spirit. I've often seen people healed when the elders of the church I pastor, Forest Hill, operate in this ministry.
I think it should be a ministry of every church of Jesus Christ. Jesus commanded the Twelve to do it. They did. And many sick were healed.
May the God of healing be your healer today.