(13) Then certain of the vagabond Jews, exorcists, took upon them to call over them which had evil spirits the name of the Lord Jesus, saying, We adjure you by Jesus whom Paul preacheth.
(14) And there were seven sons of one Sceva, a Jew, and chief of the priests, which did so.
(15) And the evil spirit answered and said, Jesus I know, and Paul I know; but who are ye?
(16) And the man in whom the evil spirit was leaped on them, and overcame them, and prevailed against them, so that they fled out of that house naked and wounded.
Another incident that shows this is in Mark 9:14-29.
(28) And when he was come into the house, his disciples asked him privately, Why could not we cast him out?
(29) And he said unto them, This kind can come forth by nothing, but by prayer and fasting.
No, it is not magic, but it is power. We don't need to go though rituals and meaningless repetitions to receive blessings from God. Only our Adversary, the devil, requires that. Once, I asked a friend if he wanted me to minister healing to him. He told me that he has already burned a few candles and appealed to some dead people. I tried to tell him that God didn't really work that way. God expects us to talk directly to Him in prayer.
(12) Verily, verily, I say unto you, He that believeth on me, the works that I do shall he do also; and greater works than these shall he do; because I go unto my Father.
(13) And whatsoever ye shall ask in my name, that will I do, that the Father may be glorified in the Son.
(14) If ye shall ask any thing in my name, I will do it.