John 13:10

Jesus says to him, He that has been washed needeth not but to wash his feet, but is clean throughout. Observe that Christ here alludes to those who wash themselves in the baths and go out washed all over, but, walking barefoot on the ground soil their feet and therefore afterwards wash them only. Again, observe that Christ, as His wont is, here rises from the corporal to the spiritual washing thus He that has been spiritually washed by baptism, as I, 0 apostles, have washed you, or he who has been washed by Contrition and penance, such an one is washed all over in soul, but needs only to wash his feet, that is, purge frequently by contrition, bodily austerities, and the like virtues, the inclinations of the soul which is stained by contact with the things of earth, and contact from their slight impurities, and this is especially needful before receiving the Holy Eucharist.

SS. Augustine, Bede, Rupert, and S. Bernard in his Sermon on the Lord's Supper, interpret more or less to this effect.

So Christ by this washing of feet purged away the sins of Peter and the apostles, especially their venial sins; for by means of this act of self-abasement He pricked their consciences and reminded them of that inward purification that must be made in the soul by contrition by means of which venial sins are expiated.

Lastly, S. Augustine in his 108th Letter to Seleucianus, gathers with some probability from the words "he that has been washed," that Peter and the apostles had been baptized before the Eucharist; both because no one is qualified to receive the Eucharist without having been baptized, and also because Christ baptized them before His death, for after His death He baptized no one, and it is clear that they must all have been baptized either by Christ Himself or by others in His behalf. The expression appears to be rightly applicable to the washing which takes place in baptism.

And ye are clean, but not all. Christ secretly strives to provoke Judas to think better of his plot of wicked treason; still He would not mention him by name, lest He should bring him into bad odour, and the apostles should rise up against him as a traitor, and ill-use him.