Charles Spurgeon Commentary Mark 9:22-25

"And oft-times it hath cast him both into the fire and into the waters, to destroy him: but if thou canst do anything, have compassion on us, and help us. And Jesus said unto him, If thou canst! All things are possible to him that believeth. Straightway the father of the child cried out, and said, I believe; help thou mine unbelief. And when Jesus saw that a multitude came running together, he rebuked the unclean spirit, saying unto him, Thou dumb and deaf spirit, I command thee, come out of him, and enter no more into him." — Mark 9:22-25 (ASV)

And ofttimes it hath cast him into the fire, and into the waters, to destroy him: but if thou canst do anything, have compassion on us, and help us. Jesus said unto him, If thou canst believe, all things are possible to him that believeth. And straightway the father of the child cried out, and said with tears, Lord, I believe; help thou mine unbelief. When Jesus saw that the people came running together, he rebuked the foul spirit, saying unto him, Thou dumb and deaf spirit, I charge thee, come out of him, and enter no more into him.

That is one way in which Christ cures. When he drives the devil out of a man, he adds, Enter no more into him. I believe in the final perseverance of the saints, because I believe in the omnipotent ejection of Satan out of men, when Christ speaks the word, Come out of him, and enter no more into him.