Catechism of the Catholic Church
“In the Old Covenant bread and wine were offered in sacrifice among the first fruits of the earth as a sign of grateful acknowledgment to the Creator. But they also received a new significance in the context of the Exodus: the unleavened bread that Israel eats every year at Passover commemorates the haste of the departure that liberated them from Egypt; the remembrance of the manna in the desert will always recall to Israel that it lives by the bread of the Word of God; their daily bread is the fruit of the promised land, the pledge of God’s faithfulness to his promises.”
Source: Catechism of the Catholic Church #1334