Real presence of Christ in the Eucharist in the context of "Blood of Christ"

In Reformed theology, the Lord's Supper or Eucharist is a sacrament that spiritually nourishes Christians and strengthens their union with Christ. The outward or physical action of the sacrament is eating bread and drinking wine. Reformed confessions, which are official statements of the beliefs of Reformed churches, teach that Christ's body and blood are really present in the sacrament and that believers receive, in the words of the Belgic Confession, "the proper and natural body and the proper blood of Christ." The primary difference between the Reformed doctrine and that of Catholic and Lutheran Christians is that for the Reformed, this presence is believed to be communicated in a spiritual manner by faith rather than by oral consumption. The Reformed doctrine of real presence is called "pneumatic presence" (from pneuma, a Greek word for "spirit"; alternatively called "spiritual real presence" or "mystical real presence").

Early Reformed theologians such as John Calvin and Heinrich Bullinger taught that Christ's person, including his body and blood, are presented to Christians who partake of it in faith. This view of the real spiritual presence was formally formulated by both Calvin and Bullinger in the Consensus Tigurinus. The historic Reformed confessions of faith, including the Second Helvetic Confession (Continental Reformed), Westminster Confession (Presbyterian), Thirty-Nine Articles (Anglican), and Savoy Declaration (Congregationalist), hold to the doctrine of real spiritual presence.

Transubstantiation (Latin: transubstantiatio; Greek: μετουσίωσις, romanized: metousiosis) is, according to the teaching of the Catholic Church, "the change of the whole substance of bread into the substance of the Body of Christ and of the whole substance of wine into the substance of the Blood of Christ". This change is brought about in the eucharistic prayer through the efficacy of the word of Christ and by the action of the Holy Spirit. However, "the outward characteristics of bread and wine, that is the 'eucharistic species', remain unaltered". In this teaching, the notions of "substance" and "transubstantiation" are not linked with any particular theory of metaphysics.

The Catholic Church teaches that, in the Eucharistic offering, bread and wine are changed into the body and blood of Christ. The affirmation of this doctrine on the real presence of Christ in the Eucharist was expressed, using the word "transubstantiate", by the Fourth Council of the Lateran in 1215. It was later challenged by various 14th-century reformers, John Wycliffe in particular.

Eucharist (Koine Greek: εὐχαριστία, romanized: eucharistía, lit. 'thanksgiving') is the name that Catholic Christians give to the sacrament by which, according to their belief, the body and blood of Christ are present in the bread and wine consecrated during the Catholic eucharistic liturgy, generally known as the Mass. The definition of the Eucharist in the 1983 Code of Canon Law as the sacrament where Christ himself “is contained, offered, and received” points to the three aspects of the Eucharist according to Catholic theology: the real presence of Christ in the Eucharist, Holy Communion, and the holy sacrifice of the Mass.

The name Eucharist comes from the Greek word eucharistia which means 'thanksgiving" and which refers to the accounts of the last supper in Matthew 26:26–28, Mark 14:22–24, Luke 22:19–20 and 1 Corinthians 11:23–29, all of which narrate that Jesus "gave thanks" as he took the bread and the wine.

In the Lutheran Churches, the Eucharist (also called the Mass, the Sacrament of the Altar, the Lord's Supper, the Lord's Table, Holy Communion, the Breaking of the Bread, and the Blessed Sacrament) refers to the liturgical commemoration of the Last Supper. Lutherans believe in the real presence of Christ in the Eucharist, affirming the doctrine of sacramental union, "in which the body and blood of Christ are truly and substantially (vere et substantialiter) present, offered, and received with the bread and wine."

A tabernacle or a sacrament house is a fixed, locked box in which the Eucharist (consecrated communion hosts) is stored as part of the "reserved sacrament" rite. A container for the same purpose, which is set directly into a wall, is called an aumbry.

Within Catholicism, Eastern Orthodoxy, and in some traditions of Lutheranism and Anglicanism, the tabernacle is a box-like or dome-like vessel for the exclusive reservation of the consecrated Eucharist. It is normally made from precious metals, stone or wood, and is lockable and secured to the altar or adjacent wall to prevent the consecrated elements within from being removed without authorization. These denominations believe that the Eucharist contains the real presence of Jesus, and thus use the term tabernacle, a word referring to the Old Testament tabernacle, which was the locus of God's presence among the Jewish people.

In the Catholic Church, a Eucharistic congress is a gathering of clergy, religious, and laity to bear witness to the real presence of Jesus in the Eucharist, which is an important Catholic doctrine. Congresses bring together people from a wide area, and typically involve large open-air Masses, Eucharistic adoration (Blessed Sacrament), and other devotional ceremonies held over several days. Congresses may both refer to National (varies by country) and International Eucharistic Congresses.

On 28 November 1897, Pope Leo XIII proclaimed Saint Paschal Baylón patron of Eucharistic Congresses and Associations.