Charles Ellicott Commentary Mark 9:23

"And Jesus said unto him, If thou canst! All things are possible to him that believeth." — Mark 9:23 (ASV)

If you can believe.—The better manuscripts omit the word “believe,” and the sentence without it is taken as expressing the sadness of surprise. Our Lord repeats the half-believing, half-despairing words of the father in a tone of sadness, If you can... Was this the way in which a man should speak who came to Him as a Healer? Such a one had to learn the great primary lesson that all things were possible to him that believeth, that the secret of previous failure lay, in part at least, in his own want of faith, as well as in that of the scribes and disciples who had tried their arts of exorcism in vain.