Bede

And they were afraid as they entered into the cloud, and a voice came from the cloud, saying: This is my beloved Son, hear him. Human fragility cannot bear the sight of greater glory, and trembling with the whole mind and body, it falls to the ground. The more one seeks greater things, the more he collapses to lower things, if he does not know his own measure. Indeed, the voice of the Father speaking from heaven is heard, which bears witness to the Son, and teaches Peter the truth, removing his error, and indeed teaches the other apostles through Peter. This is (he says) my beloved Son, it is he who should have a tabernacle built, it is him who should be obeyed. This is the Son; Moses and Elijah are servants to him, they too should prepare a tabernacle for the Lord in the inner rooms of their hearts along with you. And note, just as when the Lord was baptized in the Jordan, so also on the glorified mountain, the mystery of the whole Trinity is declared, whose glory we confess in baptism, and which we will see in the resurrection. Nor is it in vain that the Holy Spirit appears here in a bright cloud, there in a dove, because he who now keeps the faith which he perceives with a simple heart, will then behold what he had believed with the clear light of vision, and by the same grace will be protected forever.

Certain places accord with certain events. On the Mount our Lord prays, is transfigured, reveals the secrets of His glory to His disciples; as He descends to the lower parts, He is received by a large concourse. As it is said, And it came to pass, that on the next day, when he was come down from the hill, much people met him. Above He makes known the voice of the Father, below He expels the evil spirits. Hence it follows, And, behold, a man of the company cried out, saying, Master, I beseech thee look upon my son.

Not that weariness has overcome His patience, but after the manner of a physician, when he sees a sick man acting contrary to his commands, he says, 'How long shall I come to thy house, when I order one thing, you do another. But to prove that He was not angry with the man, but with the sin, He immediately added, Bring thy son hither.

Now in a mystical manner in proportion to their deserts docs our Lord daily ascend to some men, seeing that the perfect and those whose conversation is in heaven, He glorifies by exalting higher, instructing them in things eternal, and teaching them things which can not be heard by the multitude, but to others he descends, in that He strengthens the earthly and foolish men, teaching and chastening them. Now this demoniac Matthew calls a lunatic; Mark, deaf and dumb. (Matt. 17:15, Mark 9:25.) Matthew signifies those who change as the moon, increasing and decreasing through different vices, Mark those who are dumb in not confessing the faith, deaf in not hearing the very word of faith. While the boy is coming to our Lord, he is dashed to the ground; because men when turned to the Lord are often grievously afflicted by the devil, that he may instil a hatred of virtue, or revenge the injury of his expulsion. As in the beginning of the Church he waged as many fierce conflicts as he had to bewail losses suddenly brought upon His kingdom. But our Lord rebukes not the boy who suffered violence, but the evil spirit who inflicted it; for he who desires to correct the sinner, ought by reproof and abhorrence to drive away the vice, but to revive the man by gentleness, until he can restore him to the spiritual father of the Church.

And it happened on the following day, as they were descending from the mountain, a great crowd met Him, and behold, a man from the crowd shouted out, saying: Master, I beseech You, look upon my son, for he is my only one. The places match the events: On the mountain, the Lord prays, is transformed, reveals to the disciples the secrets of His majesty; descending to the lower places, He is met by the crowd, struck by the lamentation of the wretched. Above, He reveals the mysteries of the kingdom to the disciples; below, He reproaches the crowds for the sins of unbelief. Above, He discloses the Father's voice to those who could follow Him; below, He expels wicked spirits from those who were being tormented. Even now, according to the quality of merits, He ceases not to ascend and descend for some. For those who are still earthly and beginners, as if seeking the low places, He strengthens, teaches, and corrects; but the perfect, whose conversation is in the heavens, He glorifies by exalting more highly, instructs more freely about eternal things, and often teaches those things which the crowds cannot even hear.

But a thought entered among them about who was the greatest among them. Because they had seen Peter, James, and John being taken up the mountain separately, and believed some mystery was revealed to them there; and also because the keys of the kingdom of heaven had been promised to Peter earlier, and that the Church was to be built upon him, they thought either these three were preferred over the others, or among all the apostles, Peter was preeminent. There are those who think this thought was stirred in the disciples by the fact that the Lord, according to Matthew, took a coin from the mouth of a fish and gave it to those who collected the tribute for himself and Peter, as if implying that they were superior to the others, since Peter was equated with the Lord in the obligation to pay the tribute. However, a diligent reader will find this question among them happened even before the tribute coin was collected. Matthew records this event in Capernaum. But Mark says: "And they came to Capernaum. When they were in the house, he asked them, 'What were you discussing on the way?' But they were silent. For on the way they had argued with one another about who was the greatest" (Mark IX). Whether this was the occasion or some other, or both, possibly prompted, Jesus, seeing their thoughts and understanding the causes of their error, wants to heal their desire for glory with the remedy of humility.

Or, because they saw Peter, James, and John, taken apart to the mount, and the keys of the kingdom of heaven promised to Peter, they were angry that these three, or Peter, should have precedence over all; or because in the payment of the tribute they saw Peter made equal to the Lord, they supposed he was to be placed before the rest. But the attentive reader will find that the question was raised among them before the payment of the penny. For in truth Matthew relates that this took place at Capernaum; but Mark says, And he came to Capernaum, and being in the house, he asked them, What was it that ye disputed among yourselves in the way? But they held their peace; for by the way they had disputed among themselves who should be the greatest. (Mat. 18:24, Mark 9:33.)

Now herein He either teaches, that the poor of Christ are to be received by those who wish to be greater simply for His honour, or He persuades men that they are children in malice. Hence when He said, Whoever shall receive that child, he adds, in my name; that in truth they may pursue with diligence and reason for Christ's name that form of virtue which the child observes, with only nature for its guide. But because He also teaches that He is received in the child, and He Himself was born unto us a child; lest it should be thought that this was all which was seen, He subjoined, And whoever shall receive me, receiveth him that sent me; wishing verily to be believed, that as was the Father, such and so great was He.

Therefore in heretics and false catholics, it becomes us to abhor, and forbid not the common sacraments in which they are with us, and not against us, but the divisions contrary to peace and truth, wherein they are against us as following not the Lord.