Palm Sunday is "a great and holy day as it commemorates the last triumph of Our Lord Jesus Christ on earth and opens Holy Week. On this day, the Church celebrates the triumphant entry of Our Lord into Jerusalem; when the multitude, going before and following after Him, cut off branches from the trees and strewed then in His way, shouting, "Hosanna (glory and praise) to the Son of David. Blessed is He that cometh in the Name of the Lord." It is the commemoration of this triumph that palms are blessed and borne in solemn procession."
"In fact, this Palm Sunday triumph of Our Lord only led to His death. But we know that this death was not a failure. It was through His Passion and Death that He conquered the world and entered into His Kingdom. 'If I be lifted up ... will draw all things to myself" (John 12:32) ... This triumphal beginning to Holy Week is full of meaning. Although the purple Mass vestments and the Gospel of the Passion remind us that the Cross lies ahead, we alreadty know that this is the means of victory. So the Church asks us to begin Holy Week by joyfully and publicly acknowledging Christ the King." - Roman Missal 1962
Psalm 146 (147) - Chanted during the Procession of Palms
Listen to the psalm triumphantly sung here.