John 13:25

What man, then, of sound mind can possibly suppose that they were ignorant of anything, whom the Lord ordained to be masters (or teachers), keeping them, as He did, inseparable (from Himself) in their attendance, in their discipleship, in their society, to whom, "when they were alone, He used to expound" all things which were obscure, telling them that "to them it was given to know those mysteries," which it was not permitted the people to understand? Was anything withheld from the knowledge of Peter, who is called "the rock on which the church should be built," who also obtained "the keys of the kingdom of heaven," with the power of "loosing and binding in heaven and on earth? " Was anything, again, concealed from John, the Lord's most beloved disciple, who used to lean on His breast to whom alone the Lord pointed Judas out as the traitor, whom He commended to Mary as a son in His own stead? Of what could He have meant those to be ignorant, to whom He even exhibited His own glory with Moses and Elias, and the Father's voice moreover, from heaven? Not as if He thus disapproved of all the rest, but because "by three witnesses must every word be established.

John, by reclining on the Word and resting on more mystical things, was reclining in the bosom of the Word, analogous also to the Word being in the bosom of the Father, according to the statement, “The only-begotten God who is in the bosom of the Father, he has declared him.”

(t. xxxii. 13.) He then lying on Jesus' breast, saith unto Him, Lord, who is it?

While all were trembling, and not excepting even Peter, their head, John, as the beloved disciple, lay upon Jesus' breast. He then lying on Jesus' breast saith unto Him, Lord, who is it?

"When Jesus had thus said, He was troubled in spirit, and testified, and said, Verily, verily, I say unto you, that one of you shall betray Me."

Again He bringeth fear on all by not mentioning the traitor by name. "But they are in doubt"; although conscious to themselves of nothing evil; but they deemed the declaration of Christ more to be believed than their own thoughts. Wherefore they "looked one on another." By laying the whole upon one, Jesus would have cut short their fear, but by adding, "one of you," He troubled all. What then? The rest looked upon one another; but the ever fervent Peter "beckoneth" to John. Since he had been before rebuked, and when Christ desired to wash him would have hindered Him, and since he is everywhere found moved indeed by love, yet blamed; being on this account afraid, he neither kept quiet, nor did he speak, but wished to gain information by means of John. But it is a question worth asking, why when all were distressed, and trembling, when their leader was afraid, John like one at ease leans on Jesus' bosom, and not only leans, but even lies on His breast? Nor is this the only thing worthy of enquiry, but that also which follows. What is that? What he saith of himself, "Whom Jesus loved." Why did no one else say this of himself? Yet the others were loved too. But he more than any. And if no other hath said this about him, but he about himself, it is nothing wonderful. Paul too does the same when occasion calls, saying thus, "I knew a man fourteen years ago"; yet in fact he has gone through other no trifling praises of himself.

(Tr. lx. 4) On Jesus' breast; the same as in Jesus' bosom. Or, he lay first in Jesus' bosom, and then ascended higher, and lay upon His breast; as if, had he remained lying in His bosom, and not ascended to lie on His breast, our Lord would not have told him what Peter wanted to know. By his lying at last on Jesus' breast, is expressed that greater and more abundant grace, which made him Jesus' special disciple.

The Evangelist tells us that he was himself the object of special honor and love on the part of Christ our Savior. He reclines next to Jesus, actually in the very bosom of the Lord, considering this a token of Christ's surpassing affection toward him. Those who are pure in heart are most especially near to God and in the highest place of honor. For the Savior himself assigns them this conspicuous honor when he says that the pure in heart shall be blessed for they shall see God. … To those who keep their mind unstained by the world and from an empty preoccupation with the things of this life, it does seem that Christ reveals his own peculiar glory by a subtle and perhaps incomprehensible process, thereby showing also the glory of the Father, which must be what Jesus meant when he said, "Whoever has seen me has seen the Father."

Notice again how effectually the very wise Evangelist spurs us on to a desire to live, as far as possible, in the manner most accordant with reason, and to train up the keenness of our intellectual powers so as to be able, and that with perfect ease, to act in obedience to the Divine intentions, and to endeavour, as far as in us lies, to thoroughly fulfil the conditions of the vision of God. He tells us that he was himself the object of special honour and love on the part of Christ our Saviour, so as even to recline next Him, actually in the very bosom of the Lord, deeming this circumstance a token of His surpassing affection towards him. Nearest therefore to God, and as it were in the highest place in His honour, will most especially be those whose heart is pure: and to them also the Saviour Himself assigns conspicuous honour when He says that the pure in heart shall be blessed, for they shall see God. And we shall bring forward, as evidence of the truth of this saying, even this very wise Evangelist himself. For he has seen the glory of Christ, according to his own words, for he says: I beheld His glory, the glory as of the Only-begotten of the Father, full of grace and truth. For surely not with bodily eyes could any one gaze at the nature of Him Who to every creature is absolutely invisible. For, according to the Saviour's words: No man hath seen the Father, save He Which is from God, that is, the Son; He hath seen the Father. To those however who keep their mind untainted by worldly stain, and freed from vain imagination whose only concern is with this life, it seems that Christ reveals His own peculiar glory by a subtle and perhaps incomprehensible process, thereby showing forth also the glory of the Father. For it must have been with this meaning that He said: He that hath seen Me hath seen the Father.

Why then does John lean upon the breast of Jesus so irreverently and indecorously? Because he did not yet understand anything great about Christ, and they had not been taught to render fitting honor to those deserving of respect, for they were fishermen and unversed in propriety.
The Lord allows him to recline upon His breast in order to ease his sorrow, to calm the disturbance in his soul, and in general to soothe his grief. For it was natural that much sorrow was expressed on their faces as well.

Then when he says, So lying thus, close to the breast of Jesus, he said to him, Lord, who is it? he mentions the question. Note that when Peter was beckoning to John to get him to question our Lord, John was leaning near the lap of Jesus. But now when John asks he is near the breast of Jesus, for the breast is closer to the mouth than the lap is. And so John moved from the lap of Christ to his breast so he could hear his answer more quietly and privately.

As for the mystical interpretation, we can see from this that the more a person wants to grasp the secrets of divine wisdom, the more he should try to get closer to Christ, according to: "Come to him and be enlightened" (Ps 34:5). For the secrets of divine wisdom are especially revealed to those who are joined to God by love: "He shows his friend that it is his possession" (Job 36:33); "His friend comes and searches into him" (Prv 18:17).