New Defender's Study Bible Notes
9:29 prayer and fasting. The words “and fasting” were apparently dropped (or possibly added) from (or to) the original account, since a few of the ancient manuscripts do not have them. In any case, the Lord was stressing that this type of demonic possession, combined with actual illness (probably epilepsy, combined with deafness and dumbness), continuing ever since childhood, was extremely difficult and required intense, long-continued, believing prayer. Fasting would almost inevitably accompany such single-minded prayer. Christ Himself, as omnipotent Creator, was not so limited, however, and could respond instantly to the father’s earnest faith and sincere desire for stronger faith.