Luke 22:7

But should any one say, "If on the first day of unleavened bread the disciples of our Saviour prepare the Passover, on that day then should we also celebrate the Passover;" we answer, that this was not an admonition, but a history of the fact. It is what took place at the time of the saving Passion; but it is one thing to relate past events, another to sanction and leave them an ordinance to posterity. Moreover, the Saviour did not keep His Passover with the Jews at the time that they sacrificed the lamb. For they did this on the Preparation, when our Lord suffered. Therefore they entered not into the hall of Pilate, that they might not be defiled, but might eat the Passover. (John 18:28.) For from the time that they conspired against the truth, they drove far from them the Word of truth. Nor on the first day of unleavened bread, on which the Passover ought to be sacrificed, did they eat their accustomed Passover, for they were intent upon something else, but on the day after, which was the second of unleavened bread. But our Lord on the first day of unleavened bread, that is, on the fifth day of the week, kept the Passover with His disciples.

By the day of unleavened bread of the Passover, He means the fourteenth day of the first month, the day on which, having put away the leaven, they were accustomed to hold the Passover, that is, the lamb, towards evening.

To explain this Passover, the Apostle says, Christ our Passover is sacrificed for us. (1 Cor. 5:7.) Which Passover in truth must needs have been slain there, as it was so ordained by the Father's counsel and determination. And thus although on the next day, that is, the fifteenth, He was crucified, yet, on this night on which the lamb was slain by the Jews, being seized and bound, He consecrated the beginning of His sacrifice, that is, of His Passion.

Now on the same fifth day He sends two of His disciples to prepare the Passover, namely, Peter and John, the one in truth as loving, the other as loved. In all things showing, that even to the end of His life He opposed not the law. And He sends them to a strange house; for He and His disciples had no house, else would He have kept the Passover in one of them. So it is added, And they said, Where will thou that we prepare? He sends them for this reason to an unknown man: to show them that He voluntarily underwent His Passion, since He who so swayed the mind of one unknown to Him, that He should receive them, was able to deal with the Jews just as He wished. But some say that He gave not the name of the man, lest the traitor knowing his name might open the house to the Pharisees, and they should have come and taken Him before that the supper was eaten, and He had delivered the spiritual mysteries to His disciples. But He directs them by particular signs to a certain house; whence it follows, And ye shall say to the goodman of the house, The Master saith, Where is the guestchamber, &c. And he will show you an upper room, &c. By the day of unleavened bread, we must understand that conversation which is wholly in the light of the Spirit, having lost all trace of the old corruption of Adam's first transgression. And living in this conversation, it becomes us to rejoice in the mysteries of Christ. Now these mysteries Peter and John prepare, that is, action and contemplation, fervid zeal and peaceful meekness. And these preparers a certain man meets, because in what we have just mentioned, lies the condition of man who was created after the image of God. And he carries a pitcher of water, which signifies the grace of the Holy Spirit. But the pitcher is humbleness of heart; for He giveth grace to the humble, who know themselves to be but earth and dust.