The mighty power - This majesty of God, μεγαλειοτητι του Θεου. They plainly saw that it was a case in which any power inferior to that of God could be of no avail; and they were deeply struck with the majesty of God manifested in the conduct of the blessed Jesus.

(8) And they were all amazed at the mighty power of God. But while they wondered every one at all things which Jesus did, he said unto his disciples,
(8) We have no reason to promise ourselves rest and quietness in this world, seeing that they themselves who seemed to fawn upon Christ crucify him shortly after.

And they were all amazed at the mighty power of God,.... Or at "the greatness", or "majesty of God"; which was displayed in this cure: for the great power of God was manifestly seen in it, to the astonishment of the disciples, who could not cure this child, and of the parent and friends of it, and of the whole multitude: and to the confusion of the Scribes and Pharisees:
but while they wondered every one, at all things which Jesus did; and were applauding him for them, and speaking in his praise on account of them:
he said unto his disciples; privately, when they were alone together, the following words, that he might not seem to be lifted up with the praise of men; and also to show their inconstancy, that those who, now admired him, would one day crucify him; and to take off the thoughts of the disciples from a temporal kingdom and glory, they were so much in expectation of, and which every miracle of Christ, and the applause he got thereby among men, strengthened them in.

This prediction of Christ's sufferings was plain enough, but the disciples would not understand it, because it agreed not with their notions. A little child is the emblem by which Christ teaches us simplicity and humility. What greater honour can any man attain to in this world, than to be received by men as a messenger of God and Christ; and to have God and Christ own themselves received and welcomed in him! If ever any society of Christians in this world, had reason to silence those not of their own communion, the twelve disciples at this time had; yet Christ warned them not to do the like again. Those may be found faithful followers of Christ, and may be accepted of him, who do not follow with us.

DEMONIAC AND LUNATIC BOY HEALED--CHRIST'S SECOND EXPLICIT ANNOUNCEMENT OF HIS DEATH AND RESURRECTION. (Luke 9:37-45)
the mighty power of God--"the majesty" or "mightiness" of God in this last miracle, the transfiguration, &c.: the divine grandeur of Christ rising upon them daily. By comparing Matthew 17:22, and Mark 9:30, we gather that this had been the subject of conversation between the Twelve and their Master as they journeyed along.

For this second statement of the Lord's suffering at Jerusalem, see notes on Matthew 17:22-23 and Mark 9:31-32.