Contradiction with Matthew 17:19
This verse also describes the disciples' inability to cast out a demon, but it emphasizes lack of faith as the reason, providing a different emphasis compared to Mark 9:28 where the discussion is not about faith when the disciples ask why they couldn't cast it out.
Matthew 17:19: Then came the disciples to Jesus apart, and said, Why could not we cast him out?
Contradiction with James 5:16
This verse emphasizes the effectiveness of prayer in healing and changing situations, potentially contradicting the implication in Mark 9:28 where the disciples' previous attempts to cast out the demon were unsuccessful, raising questions about the efficacy of their prayers.
James 5:16: Confess [your] faults one to another, and pray one for another, that ye may be healed. The effectual fervent prayer of a righteous man availeth much.