Mark 9:5

Peter had forgotten that the glorious kingdom of Christ was not of this world, but in heaven only; that himself and the other apostles, clothed as they were with their mortality, could not participate in immortal joys; and that the mansions in the house of the Father are not raised with human hands. He again shewed that he knew not what he said, by wishing to make three tabernacles, one for the law, one for the prophets, and one for the gospel, since these three cannot be separated from each other. (Ven. Bede)

5. The great delight that the disciples took in seeing this sight, and hearing this discourse, is expressed by Peter, the mouth of the rest; He said, Master, it is good for us to be here, v. 5. Though Christ was transfigured, and was in discourse with Moses and Elias, yet he gave Peter leave to speak to him, and to be as free with him as he used to be. Note, Our Lord Jesus, in his exaltation and glory, doth not at all abate of his condescending kindness to his people. Many, when they are in their greatness, oblige their friends to keep their distance; but even to the glorified Jesus true believers have access with boldness, and freedom of speech with him. Even in this heavenly discourse there was room for Peter to put in a word; and this is it, "Lord, it is good to be here, it is good for us to be here; here let us make tabernacles; let this be our rest for ever." Note, Gracious souls reckon it good to be in communion with Christ, good to be near him, good to be in the mount with him, though it be a cold and solitary place; it is good to be here retired from the world, and alone with Christ: and if it is good to be with Christ transfigured only upon a mountain with Moses and Elias, how good it will be to be with Christ glorified in heaven with all the saints! But observe, While Peter was for staying here, he forgot what need there was of the presence of Christ, and the preaching of his apostles, among the people. At this very time, the other disciples wanted them greatly, v. 14. Note, When it is well with us, we are apt to be mindless of others, and in the fulness of our enjoyments to forget the necessities of our brethren; it was a weakness in Peter to prefer private communion with God before public usefulness. Paul is willing to abide in the flesh, rather than depart to the mountain of glory (though that be far better), when he sees it needful for the church, Phil 1 24, 25. Peter talked of making three distinct tabernacles for Moses, Elias, and Christ, which was not well-contrived; for such a perfect harmony there is between the law, the prophets, and the gospel, that one tabernacle will hold them all; they dwell together in unity. But whatever was incongruous in what he said, he may be excused, for they were all sore afraid; and he, for his part, wist not what to say (v. 6), not knowing what would be the end thereof.

Verses 1-13 Here is a prediction of the near approach Christ's kingdom. A glimpse of that kingdom was given in the transfiguration of Christ. It is good to be away from the world, and alone with Christ: and how good to be with Christ glorified in heaven with all the saints! But when it is well with us, we are apt not to care for others, and in the fulness of our enjoyments, we forget the many wants of our brethren. God owns Jesus, and accepts him as his beloved Son, and is ready to accept us in him. Therefore we must own and accept him as our beloved Saviour, and must give up ourselves to be ruled by him. Christ does not leave the soul, when joys and comforts leave it. Jesus explained to the disciples the prophecy about Elias. This was very suitable to the ill usage of John Baptist.