Question: Why do priests insist on giving Holy Communion from the tabernacle instead consecrating Hosts for those who want to receive at each Mass? I feel that I receive greater graces by means of this closer participation in the Mass.
Answer: The most likely reason that a priest might communicate the faithful with Hosts from the tabernacle during Mass is to ensure that there are enough accommodate everyone wishing to receive our Lord in Holy Communion. In many churches the number receiving may vary widely from Mass to Mass. The simplest way of dealing with this variability is to keep one or more *ciboria full of consecrated Hosts in the tabernacle at all times.
We receive the entire Body and Blood, Soul and Divinity of Jesus Christ in any consecrated Host (or in the tiniest fragment of a Host or drop of the Precious Blood) we receive. This is true no matter when the Host was consecrated, as long as It remains incorrupt. In modern times this essential truth of the Real Presence has been denied by those Modernists who hold that our Lord is present only while "the people celebrate the Eucharist," and only when Communion is received under both forms. Combatting this error, borrowed from Protestantism, may be an additional reason why many traditional priests distribute previously consecrated Hosts.
It it true, however, that the faithful may derive additional graces through close union with the action of the priest in the Mass. This union may be fostered through various means, including the reception of a Host consecrated during the Mass in question. Pope Pius XII, citing his predecessor, Pope Benedict XIV, tells us that:
The faithful should understand, though, that there may be times when it will be necessary for the priest to distribute those Hosts which are reserved. For example, it may be necessary in order to accommodate a large or unexpected number of communicants, or to ensure that the Hosts in the tabernacle are not subject to the danger of deterioration. Pope Pius assures us that such communicants fully participate in the Holy Sacrifice. (ibid., 122)
Those who receive the Body and Blood of our Lord in Holy Communion are always invited and advised to deepen their participation in the Mass by spending some time with Him in thanksgiving, even after the Mass itself is finished.
Admittedly the congregation has been officially dismissed, but each individual, since he is united with Christ, should not interrupt the hymn of praise in his own soul "always returning thanks for all in the name of our Lord Jesus Christ, to God the Father." (ibid., 124)
* The consecrated Hosts are kept in the tabernacle in a vessel shaped like a chalice and having a tight fitting cover. It is called a "ciborium" from the Latin word "cibus," meaning "food." The plural is "ciboria."