During Mass, why does the priest pour water into the wine and put a piece of the consecrated Host into the chalice?
These actions are very ancient and began as practical necessities, but eventually the necessities disappeared and were even forgotten. In the ancient world, the Greeks added water to wine because it was often thick, gritty and too strong. It was simply good taste to add water to wine before drinking it. The Romans loved all things Greek, so they adopted Greek manners and spread them to the lands they conquered. And even though it was not originally a Jewish custom to add water to wine, it soon became part of the Passover meal itself and hence part of our Mass.
As early as the fourth century, catechists explained that the water represented humanity of Christ and the wine, divinity of Christ. Once you put the water into the wine, it’s impossible to take it out again. Because of Jesus, humanity can never again be separated permanently from God. So the custom continues today as the priest or deacon pray the following prayer during this gesture: “By the mystery of this water and wine may we come to share in the divinity of Christ who humbled himself to share in our humanity.”
The practice of dropping a piece of the consecrated Host into the chalice may have started because of the ancient Roman custom known as fermentum. Christians in the suburbs of the Roman Empire could not always travel to Rome for Eucharist. So when the bishop broke the bread before Communion, he would set aside a piece for each missing congregation. A minister of the Eucharist brought this fermentum to each suburban church later, where the priest would drop it into the chalice to be consumed by everyone in the congregation during the communion rite. Thus, the bishop’s Eucharist “fermented” this celebration. Eventually, the pope also began to set aside a piece for this next celebration. This was called the sacra, and it, too, was added to the chalice to show that this Mass is a continuation of the one before it--the one sacrifice of Christ. Priests began imitating the pope by breaking off a piece of the bread just consecrated. Some then explained this as a sign of Christ’s Resurrection. A body without blood is dead, but when Christ’s body is “reunited” with his blood, Christ is risen. This gesture continues to this day, as priests pray the prayer; “May this mingling of the Body and Blood of Lord Jesus Christ bring eternal life to us who receive it.”
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