“While they were eating, Jesus took bread, and when he had given thanks, he broke it and gave it to his disciples, saying, “Take and eat; this is my body.” Then he took a cup, and when he had given thanks, he gave it to them, saying, “Drink from it, all of you. This is my blood of the covenant, which is poured out for many for the forgiveness of sins” Matthew 26:26-28.
The sacrament of the Holy Eucharist is the heart and summit of the Church’s life. In the Holy Eucharist, under the appearances of bread and wine, the Lord Christ is contained, offered, and received.
Christ instituted the Holy Eucharist in this way: He took bread, blessed and broke it, and giving it to His apostles, said: “Take and eat; this is My body;” then He took a cup of wine, blessed it, and giving it to them, said: “All of you drink of this; for this is My blood of the new covenant which is being shed for many unto the forgiveness of sins;” finally, He gave His apostles the commission: “Do this in remembrance of Me.”
When Our Lord said, “This is My body,” the entire substance of the bread was changed into His body; and when He said, “This is My blood,” the entire substance of the wine was changed into His blood. Christ could not have used clearer, more explicit words than “This is My body.” He did not say, “This is a sign of My body,” or “This represents My body,” but, “This is My body.”
Catholics take Christ at His word because He is the omnipotent God. “Truly, truly, I say to you, unless you eat the flesh of the Son of Man and drink His blood, you have no life in yourselves.” On His word they know that the Holy Eucharist is the body and blood of Christ and through this all have an Eternal life along with the God after death.