As noted in my previous reply, there are a number of places in the Bible that record Jesus' command to practice the sacrament of communion and relating the elements of bread and wine to his body and blood. However, just how literally that relationship is viewed is not agreed upon by all Christians.
Roman Catholics: The bread and wine are literally transformed into the physical body and blood of Jesus.
Lutherans: The bread and wine are not transformed, but the physical body and blood are in, with, and under them.
Reformed/Presbyterian: The bread and wine are not transformed, but we feed upon Jesus in a spiritual sense rather than physical.
Baptists and many others: The bread and wine are not transformed, but are merely representative of Jesus' body and blood, and we don't feed upon him in a physical or spiritual sense at all.