There was at the table reclining in Jesus’ bosom one of his disciples, whom Jesus loved.
Verse 23. Leaning on Jesus' bosom. This does not mean that he was at that time actually lying on his bosom, but that he occupied a situation next to him at the table, so that his head naturally fell back on his bosom when he spoke to him. . Whom Jesus loved. This was doubtless John himself.
THE TRAITOR INDICATED--HE LEAVES THE SUPPER ROOM. (Joh 13:21-30) When Jesus had thus said, he was troubled in spirit, and testified, and said, Verily, verily, I say unto you, One of you shall betray me--The announcement of Joh 13:18 seems not to have been plain enough to be quite apprehended, save by the traitor himself. He will therefore speak it out in terms not to be misunderstood.
Commenting on John 13:21-30
there was leaning on Jesus' bosom one of his disciples, whom Jesus loved--Thus modestly does our Evangelist denote himself, as reclining next to Jesus at the table. Peter . . . beckoned to him to ask who it should be of whom he spake--reclining probably at the corresponding place on the other side of Jesus.