Mark 9:25 When Jesus saw that a crowd was running to the scene, he rebuked the impure spirit. “You deaf and mute spirit,” he said, “I command you, come out of him and never enter him again.”
After God showed them things were possible beyond their imaginations, Jesus showed them things here on earth are possible for anyone who believes so.
God is able to heal the sick, but we should be able to have faith He is able!
There is not use having a knife that is sharp enough to cut anything unless it is used to cut things with.
There are good things and bad things which can be done with a knife; but God wants us to use our faith for good and His glory!