The question:
Fervr was recently asked “What authority do believers in Christ (who are indwelt by the Holy Spirit) have over sickness, demons etc?I ask this because as I look at the life of Jesus, and how we are meant to be imitating Him, this seems like it should be a part of our ministry, or should it?”
The answer:
(Answer thanks to Peter Bolt)
Believers have no authority over sickness and demons, but Jesus does. When the NT calls upon us to 'imitate Christ', this is not a call to do everything that he ever did, still less is it a promise that we will be able to. So, for example, Paul's call to imitate him as he imitates Christ (1 Corinthians 11:1) is a call to put aside our own interests in order serve others in the interests of their salvation. In this we can also remember Philippians 2:1-11.
Jesus is the one in charge, with all authority in heaven and earth. We are not called upon to imitate him in taking over his position — that would be ludicrous, and sounds very much like what Satan tempted Adam and Eve to do in Genesis 3! All authority in heaven and earth always belongs to Jesus. During his ministry he gave his 12 disciples authority to extend his ministry to Israel, and they too healed and cast out demons as a result. There was a wider group of 72 who also got involved in his ministry to Israel in this way.
But for those beyond his death and resurrection, we tap into Jesus' authority, not by imitating him, but by prayer. If we are sick or fearful of the devil, then we pray to Jesus, knowing that he is already victorious over sin, death, the devil, and he has already won an assured place for us in heaven. This will calm our fears as we put our faith in him. When we are sick, we can certainly ask for him to cure us, and sometimes he will. But every believing prayer will be 'if it is your will', and sometimes he will have lessons for us to learn by our continued sickness (as indeed in Paul's case).
Jesus' ministry to the sick and demonised of Israel (and the ministry of the 12 and the 72), was pointing ahead to the real victory he came to bring, namely, to die for our sins upon the cross and to secure for us eternal life. The really important 'authority' to tap into for ourselves now is the 'authority' to become Children of God (John 1:12-13), through faith in him. He works his authority through the word of the gospel: we die with Christ, we rise with Christ, and this transforms life in all kinds of ways. The real 'authority' we can tap into for others is to pray that they, too, become Christians as their blind eyes are made to see. This is the 'greater works' (John 5:20) that are even greater than the healing and demon-deliverances that Israel experienced when Jesus was physically present.