This one weird trick will not produce miracles (Acts 19)

So he was not able to perform any mighty deed there, apart from curing a few sick people by laying his hands on them. He was amazed at their lack of faith. (Mark 6:5-6)

So extraordinary were the mighty deeds God accomplished at the hands of Paul that when face cloths or aprons that touched his skin were applied to the sick, their diseases left them and the evil spirits came out of them. (Acts 19:11-12)

The evil spirit said to them in reply, “Jesus I recognize, Paul I know, but who are you?” (Acts 19:15)

Luke notes frequently in Acts that the preaching of the apostles was accompanied by miracles and mighty deeds. In Acts 5 Luke records that people placed the sick and lame in Peter's pathway, believing that they would be healed if only Peter's shadow fell upon them. Likewise with Paul, people applied cloths and aprons that the apostle had touched to the skin of the sick and possessed, and they were healed. 

Great was the faith of those who were healed. Throughout the New Testament, faith is described as a necessary condition for healing. God's grace, whether it brings us physical or spiritual healing, or spiritual gifts, only operates in us if we cooperate with it in faith. God does not force His grace upon us, and we can choose to harden our hearts to block the working of His grace. This was the case with the people of Nazareth who knew (or more accurately, thought they knew) Jesus and refused to accept Him as the Son of God. Jesus could not perform many miracles there not because He was suddenly powerless but because the people of Nazareth refused to cooperate with His grace. Conversely, in so many of the healing miracles of Jesus, the Lord is quick to tell the one healed, "Your faith has saved you."

Luke also provides cautionary tales in Acts about those who attempt to abuse the divine power (more specifically, the holy name of Jesus) for their personal gain. In Acts 8 a sorcerer named Simon offered to pay Peter money if he would bestow the gift of the Holy Spirit upon him. Peter denounced Simon soundly, saying "I see that you are full of bitterness and captive to sin," and Simon to his credit promptly repented. The Jewish exorcists in Acts 19 suffered a worse fate. They saw the mighty deeds accomplished through Paul and figured what worked for him might work for them. They had not been baptized; there is no indication that they had accepted Jesus as their savior or repented of their sins. They were merely seeking to use the divine power for their own fame and fortune. When they attempted to drive out an evil spirit by invoking the name of Jesus, the demon's response was devastating: “Jesus I recognize, Paul I know, but who are you?” The evil spirits in the New Testament have a vivid awareness of who their enemies are. They have no fear of non-believers.

Acts 19 is a reminder to us not to approach God in prayer as though He were a wish-granting genie (or to use a modern example, an ATM machine). The key words in our approach to God in prayer must be the words our Savior taught us: Thy will be done. God always knows what is best for us. He wants us to bring our petitions to Him in faith. He desires nothing more than our happiness. But He may delay in granting our petitions, or perhaps not grant them at all, if they do not conduce to our salvation, our growth in holiness. Our role is to pray faithfully with patience and perseverance, trusting in His mercy, and accepting His will for our lives.