Mark 14:22
And as they did eat, Jesus took bread, and blessed, and brake it, and gave to them, and said, Take, eat: this is my body. And as they did eat, Jesus took bread, and blessed, and brake it, and gave to them, and said, Take, eat: this is my body.
At the Passover meal Jesus established the Lord's Supper, instituting this service in place of the Passover as the great memorial. As they ate He took bread, blessed it, broke it, and gave it to the disciples, saying it is His body. The bread was a sign of His body and of His sacrificial self-giving, the sacrifice He was about to make in giving His life for sin. That sacrifice was for the remission of the sins of all who will believe and receive Him.
He made the supper a memorial of His sacrifice, designed to be often commemorated to bring that sacrifice to remembrance. It was to be observed by His followers in every land and age. The ordinance is not to be exclusive, but each must participate in it publicly and thus bear witness: I accept Christ as my personal Saviour, He gave His life for me that I might be rescued from death.
The ordinance was supplanted by the mass, in which priests claimed that ordinary bread and wine became Christ's actual body and blood and that they could thereby create God. The bread is not changed into Christ's actual body, and claiming power to make that change is a false and blasphemous teaching.