As my Father appointed a kingdom for me, so do I appoint for you that you may eat and drink at my table in my kingdom, and sit on thrones judging the twelve tribes of Israel. 282
Catechism number 560
Jesus' entry into Jerusalem manifested the coming of the kingdom that the King-Messiah was going to accomplish by the Passover of his Death and Resurrection. It is with the celebration of that entry on Palm Sunday that the Church's liturgy solemnly opens Holy Week.
IN BRIEF