John 13:1
“And He took His garments, and having sat down again, said unto them, Know ye what I have done to you?” And what follows.
1. A grievous thing, beloved, a grievous thing it is to come to the depths of wickedness; for then the soul becomes hard to be restored. Wherefore we should use every exertion not to be taken at all; since it is easier not to fall in, than having fallen to recover one's self. Observe, for instance, when Judas had thrown himself into sin, how great assistance he enjoyed, yet not even so was he raised. Christ said to him, “One of you is a devil”; He said, “Not all believe”; He said, “I speak not of all,” and, “I know whom I have chosen”; and not one of these sayings does he feel. Now when He had washed their feet, and taken His garments, and sat down, He said, “Know ye what I have done unto you?” He no longer addresses Himself to Peter only, but to them all.
Source: Homilies on the Gospel of John (New Advent)