Contradiction with Matthew 17:19-20
This verse suggests that the disciples can cast out demons if they have faith, which contrasts with Mark 9:25, where Jesus alone rebukes the spirit.
Matthew 17:19-20: Then came the disciples to Jesus apart, and said, Why could not we cast him out?
Contradiction with Matthew 8:29
The demons recognize Jesus and express fear, whereas in Mark 9:25, there is no dialogue or fear expressed by the spirit.
Matthew 8:29: And, behold, they cried out, saying, What have we to do with thee, Jesus, thou Son of God? art thou come hither to torment us before the time?
Contradiction with Luke 9:1
Jesus gives all the disciples power and authority over demons, yet in Mark 9:25, His power appears necessary to cast out the spirit.
Luke 9:1: Then he called his twelve disciples together, and gave them power and authority over all devils, and to cure diseases.
Contradiction with John 14:12
Jesus says believers will do greater works than He did, but in Mark 9:25, it seems the disciples are unable to perform this miracle without Jesus.
John 14:12: 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.
Contradiction with Acts 19:15-16
The evil spirit acknowledges the authority of Jesus but overpowers others, contrasting with the immediate obedience to Jesus' rebuke in Mark 9:25.
Acts 19:15-16: And the evil spirit answered and said, Jesus I know, and Paul I know; but who are ye?