The administration of communion to a dying person. It was given as sustenance for a journey. The practice of viaticum as a meal for the dead was a pagan burial custom from pre-Christian times. Communion was substituted as viaticum by the early Christians. The Christian practice of viaticum was apparently regarded as an ancient custom by the fourth century. The BCP provides a form for Communion under Special Circumstances (pp. 396-399), with communion administered from the reserved sacrament. A postcommunion prayer is included in the BCP rite for ministration to the sick (p. 457). The benefits of communion are understood to be received by a person who desires to receive the eucharist but cannot eat and drink the bread and wine because of sickness or physical disability. See Last Rites.
Glossary definitions provided courtesy of Church Publishing Incorporated, New York, NY,(All Rights reserved) from "An Episcopal Dictionary of the Church, A User Friendly Reference for Episcopalians," Don S. Armentrout and Robert Boak Slocum, editors.