Reserved sacrament

During the Liturgy of the Eucharist, the second part of the Mass, the elements of bread and wine are considered to have been changed into the veritable Body and Blood of Jesus Christ. The manner in which this occurs is referred to by the term transubstantiation, a theory of St. Thomas Aquinas, in the Roman Catholic Church. Members of the Orthodox, Lutheran, and Anglican communions also believe that Jesus Christ is really and truly present in the bread and wine, but they believe that the way in which this occurs must forever remain a sacred mystery. In many Christian churches some portion of the consecrated elements is set aside and reserved after the reception of the Holy Eucharist, referred to as the reserved sacrament. The reserved sacrament is usually stored in a tabernacle, a locked cabinet made of precious materials and usually located on, above or near the high altar. In Western Christianity usually only the Host, from Latin: hostia, meaning "victim" (the consecrated bread), is reserved.

The reasons for the reservation of the sacrament vary by tradition, but common reasons for reserving the sacrament include for it to be taken to the ill or housebound, for the devotional practice of Eucharistic Adoration, for viaticum for the dying, and so that Communion may still be administered if a priest is unavailable to celebrate the Eucharist. During the Triduum, the sacrament is taken in procession from the tabernacle, if on the high altar or otherwise in the sanctuary, to the Altar of Repose, reserved from the end of the Mass of the Lord's Supper until after the Mass of the Pre-Sanctified or the Communion Rite on Good Friday, commemorating the time between the Last Supper and the Crucifixion of Jesus. The Blessed Sacrament is then returned to the tabernacle at the end of the first Mass of the Resurrection.

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