It has long been my custom not to preach a sermon on Palm Sunday—the readings are eloquent in themselves, and of course they are rather long in the traditional rite. But I do ask you to ponder two things.
The first is the fickleness of human nature. On Palm Sunday, at the blessing of the Palms, we encounter a jubilant crowd welcoming Jesus into the holy city of Jerusalem, less than one week before that same crowd began yelling to Pontius Pilate, “Crucify Him, crucify Him ... Let His blood be upon us and our children.” We must always be on our guard, for we too share this fickleness. We can be, at one moment, the truly pious followers of our Lord, but in the next moment we can become followers of the Devil himself. We must always be on our guard.
The second thing is the connection of the Last Supper with the Sacrifice of the Cross. You don't see the connection so clearly in some of the modern abridgements of the Passion Gospels, so it is important that we read them in full, as will be done by traditional Catholics all over the world this Holy Week:
On Thursday and Friday, the actual days of the Last Supper and the Crucifixion, the Church has us read the account of the Last Supper alone (John 13: 1-15 and 1 Corinthians 11: 20-32) and has us consecrate and reserve an additional large Host, which will remain at the Altar of Repose until the priest receives It in Holy Communion at the Liturgy of the Presanctified on Good Friday after the reading of Saint John's Gospel account of the Crucifixion (John 18 & 19).
So, throughout the week we are reminded both of our own human frailty, and of the great Sacrificial action of our Lord on the Cross which is re-presented for us each time we offer the Holy Sacrifice of the Mass.
Let's listen now to Saint Matthew's account of the Last Supper and the Crucifixion.