"bestow your bread on the hungry"

hold back your foot on the sabbath
from following your own pursuits on my holy day;
If you call the sabbath a delight,
and the LORD’s holy day honorable;
If you honor it by not following your ways,
seeking your own interests, or speaking with malice
Then you shall delight in the LORD

-- Is 58:9b-14

At the heart of the Eucharistic celebration are the bread and wine that, by the words of Christ and the invocation of the Holy Spirit, become Christ's Body and Blood. Faithful to the Lord's command the Church continues to do, in his memory and until his glorious return, what he did on the eve of his Passion: "He took bread. . . ." "He took the cup filled with wine. . . ." The signs of bread and wine become, in a way surpassing understanding, the Body and Blood of Christ; they continue also to signify the goodness of creation. Thus in the Offertory we give thanks to the Creator for bread and wine, fruit of the "work of human hands," but above all as "fruit of the earth" and "of the vine" - gifts of the Creator. The Church sees in the gesture of the king-priest Melchizedek, who "brought out bread and wine," a prefiguring of her own offering.

-- CCC 1333