1 Corinthians 11:17-34

v17-22: It would be better to not participate in the Lord's Supper than to do so in a manner that is careless.

v23-34: The visible signs of the bread and the cup represent Christ's body broken and His blood shed, along with all the benefits that flow from His death and sacrifice.  At the last supper Christ "gave his disciples his body and blood along with all the benefits gained by his death, and he continues to do the same every time the sacrament is administered to true believers."