Eucharist and sin offerings
In Christian thought, Jesus offered himself on the Cross to expiate human sin. Celebration of the Eucharist with bread and wine denotes the believers' partaking of this offering of Jesus' flesh and blood. The gospels and theological interpretations draw connections to the Old Testament and Jewish sacrifice rituals.
The denominations differ in their interpretations of the Eucharist. The Catholic and Lutheran churches emphasize the "real presence" of Jesus in the substance of the wine and bread, while reformed (Calvinists) view it as a mere sign of remembrance.