Although the precise subject of this book is not the sacrifice of the Mass, it is impossible not to speak of the Mass when we speak of the Eucharist as Sacrament. The Sacrament and Sacrifice of the Eucharist are inseparable. The Real Presence of Christ in the Host is the necessary and immediate consequence of transubstantiation. But the purpose of transubstantiation is first of all to make Christ present on the altar in a state of sacrifice or immolation, by the separate consecration of the two species of Bread and Wine. At the same time the sacrifice cannot be completed without these consecrated elements being received in communion at least by the celebrating priest. Finally, the consecrated Host is kept in reserve in the tabernacle in order that the sick and others who cannot receive at the time of Mass may be able to receive the Body of Our Lord at some other time and thus have their share in the sacrifice of Christ. What we adore in our visits to the Blessed Sacrament is therefore Jesus Christ Himself, permanently present in the Host which was consecrated in the Holy Sacrifice and which will eventually be received in Communion.

The Living Bread
Thomas Merton