Matthew Poole and continuators on John 13:23

23 Now there was leaning on Jesus bosom , one of his disciples, whom Jesus loved .

This leaning on Iesus his bosom, and the lying on Iesus his breast, mentioned ver. 25. cannot be understood without the understanding of the usual posture the Iews used at their meals, and particularly, at the Paschal Supper: of which we have spoken largely in our notes upon Matth. 26.20. (see the Annotations there) Their posture seemeth to have been kneeling, and resting their bodies back upon their legs, with a leaning upon their left elbow; and this seemeth not to have been so close, but that he that so sate, might use his other hand to take his meat; hence he who sate before any, sate with his back towards him, but leaning towards the bosome of the other, which is here called a leaning on (that is towards) his bosome, and lying on his breast, for it cannot be understood of such a setting, or leaning, as to touch the others breast or bosome, for that would have hindred him upon whom the person so leaned, from any use of his right hand to take his meat or drink. It is apparent from hence, that at this Supper there was none but Christ and his twelve Disciples. Secondly, that they sate in this posture of leaning: These two things make it very probable, if not certain, that the Supper here mentioned was either the Paschal Supper, or a common Supper, which immediately went before, or followed after the Passover Supper. For 1. we have no record of any other Supper, at which were onely Christ and the twelve Disciples, and 2. if we may believe the Iewish Writers, tho their ordinary posture at their common meals was Discubiture, that is, a kneeling on their knees, with a resting their bodies backward upon their legs; yet this posture of leaning was constantly added onely upon the Passover night, as a further testimony of their liberty; that they were not now servants, (as in the land of Egypt.)

The person who sate next to our Saviour, with his back next our Saviours bosome was Iohn, often in Scripture dignified with the title of the beloved Disciple, and him whom Jesus loved, Chap. 19.26. and 20.2. and 21.7, 20.