Venerable Fulton Sheen
“The Mass, too, has an engagement which corresponds to the Offertory of the Mass, in which the faithful bring gifts of bread and wine, or its equivalent, that which buys bread and wine. As the ring is a symbol of the lover offering himself to the beloved, so too, the bread and wine are the symbols of a person offering himself to Christ. This is apparent in several ways: first, since bread and wine have traditionally nourished man and given him life, in bringing that which was the substance of his life, he is equivalently giving himself. Second, the readiness to sacrifice himself for the beloved is revealed in the bread and wine; no two substances have to undergo more to become what they are than do wheat and grapes. One passes through the Gethsemane of a mill, the other through the Calvary of the winepress before they can be presented to the Beloved on the altar. In the Offertory, therefore, under the appearance of bread and wine, the faithful are offering themselves to Christ.”
Source: Ven. Fulton Sheen, These are the Sacraments