Eucharistic theology is a branch of Christian theology which treats doctrines concerning the Holy Eucharist, also commonly known as the Lord's Supper. It exists exclusively in Christianity and related religions, as others generally do not contain a Eucharistic ceremony.In the Gospel accounts of Jesus' earthly ministry, a crowd of listeners challenges him regarding the rain of manna before he delivers the famous Bread of Life Discourse (John 6:22-59), and he describes himself as the ""True Bread from Heaven"". The aforementioned Bread of Life Discourse occurs in the Gospel of John, 6:30-59. Therein, Jesus promises to give His Flesh and Blood, which will give eternal life to all who receive It. In John 6:53, Jesus says, ""I tell you the truth, unless you eat the flesh of the Son of Man and drink his blood, you have no life in you."" And continues, (v. 54-55) ""Whoever eats my flesh and drinks my blood has eternal life, and I will raise him up at the last day. For my flesh is real food and my blood is real drink."" Every year, the nation of Israel celebrated the Passover Meal, remembering and celebrating their liberation from captivity in Egypt. It was at the Passover that Jesus Christ celebrated the Last Supper with his Apostles. Saint Paul in his First Letter to the Corinthians (1 Corinthians 11:23-26) and the Synoptic Gospels of Matthew (26:26-28), Mark (14:22-24), and Luke (22:19-20) state that Jesus, in the course of the Last Supper on the night before his death and resurrection, said: ""This is my body"", and ""This is my blood"". For instance, Matthew recounts: ""And as they were eating, Jesus took bread, and blessed it, and brake it, and gave it to the disciples, and said, Take, eat; this is my body; And he took the cup, and gave thanks, and gave it to them, saying, Drink ye all of it; For this is my blood of the new testament, which is shed for many for the remission of sins."" The Gospel of John, on the other hand, makes no mention of this. One explanation offered is that he wrote his Gospel to supplement what the other evangelists had already written.