Thomas Coke Commentary on the Holy Bible - Matthew 17:15
Matthew 17:15. For he is lunatic— Σεληνιαζεται . The English word lunatic always implies madness; but the Greek word is applied to any disease which is under the influence of the moon, such as the epilepsy, which seems to have been the distemper wherewith this man's son was afflicted by the power of the demon which possessed him. See also for this history the parallel places in St. Mark and Luke, who relate it more circumstantially than St. Matthew. read more
Coffman Commentaries on the Bible - Matthew 17:16
And I brought him to thy disciples, and they could not cure him.The latent doubt planted in the apostles' hearts by the Pharisees must surely have played a part in the inability to heal the lunatic. Their faltering faith, coupled with the double difficulty at hand, made them powerless to effect a cure. These same disciples had once returned with joy over the fact that demons were subject to them in the name of Christ (Luke 10:17ff); but then they were powerless in the presence of that lunatic... read more