Mark 9:6

(in Matt tom. xii. 40) Mark says in his own person, For he wist not what to say. Where it is matter for, consideration, whether perchance Peter spoke this in the confusion of his mind, by the motion of a spirit not his own; whether perchance that spirit himself who wished, as far as in him lay, to be a stumbling-block to Christ, so that He might shrink from that Passion, which was the saving of all men, did not here work as a seducer and wish under the colour of good to prevent Christ from condescending to men, from coming to them, and taking death upon Himself for their sakes.

CHRYSOSTOM.f Again, Peter neither comprehended that the Lord worked His transfiguration for the showing forth of His true glory, nor that He did this in order to teach men, nor that it was impossible for them to leave the multitude and dwell in the mountain. It goes on, For they were sore afraid. But this fear of theirs was one by which they were raised from their usual state of mind to one higher, and they recognised that those who appeared to them were Moses and Elias. The soul also was drawn on to a state of heavenly feeling, as though carried away from human sense by the heavenly vision.

Or else, Peter, fearing to come down from the mount because he had now a presentiment that Christ must be crucified, said, It is good for us to be here, and not to go down there, that is, in the midst of the Jews; but if they who are furious against Thee come hither, we have Moses who beat down the Egyptians, we have also Elias, who brought fire down from heaven and destroyed the five hundred.