12 Now on the first day of the unleavened bread, when they sacrificed the pasch, the disciples say to him: Whither wilt thou that we go, and prepare for thee to eat the pasch?
Chrysostom: Whilst Judas was plotting how to betray Him, the rest of the disciples were taking care of the preparation of the Passover.
Bede: He means by the first day of the Passover the fourteenth day of the first month, when they throw aside leaven, and were wont to sacrifice, that is, to kill the lamb at even. The Apostle explaining this says, “Christ our Passover is sacrificed for us” [1 Cor 5:7]. For although He was crucified on the next day, that is, on the fifteenth moon, yet on the night when the lamb was offered up, He committed to His disciples the Mysteries of His Body and Blood, which they were to celebrate.
Pseudo-Jerome: The unleavened bread which was eaten with bitterness, that is with bitter herbs, is our redemption, and the bitterness is the Passion of Our Lord.
Theophylact: From the words of the disciples, “Where wilt thou that we go?” it seems evident that Christ had no dwelling-place, and that the disciples had no houses of their own; for if so, they would have taken Him thither.
Pseudo-Jerome: They say, “Where wilt thou that we go?” to shew us that we should direct our steps according to the Will of God.
13 And he sendeth two of his disciples, and saith to them: Go ye into the city; and there shall meet you a man carrying a pitcher of water, follow him;
Augustine: Mark says a pitcher, Luke a two-handed vessel [Luke 22:10]; one points out the kind of vessel, the other the mode of carrying it; both however mean the same truth.
Bede: It is a proof of the presence of His divinity, that in speaking with His disciples, He knows what is to take place elsewhere.
Pseudo-Jerome: “Follow Him.” That is, him who leads to the lofty place, where is the refreshment prepared by Christ.
Scripture from the Douay-Rheims Bible. Commentary from St. Thomas Aquinas, Catena Aurea, Vol. II (London: Rivington, 1842).