The Holy Sacrifice of the Mass is also the Sacrament of the Mass. The Church has a right to prescribe the ceremonies of the Mass, the sacred vessels to be used, the vesture of the priest in offering Mass, and both the Biblical readings and the prayers to be recited at Mass, even though a valid Mass can be said without the observance of what we call the rubrics. However, strict observance of the rubrics, which are written in red in the liturgical books,* is necessary for the licit celebration of Mass. Also, the rubrics have very much to do with disposing the people to not just attend Mass, but to be spiritually disposed to receive the graces which Christ confers through the Holy Sacrifice.
*(The Roman Missal is the liturgical book containing all the texts, together with the norms and rubrics, of the Holy Mass. It provides for and protects the unity of worship for the whole Church, in every part of the world.)
What makes a Mass valid? The Sacrifice of the Mass is valid only if the priest or Bishop offering Mass has been validly ordained in the ministerial priesthood of the Catholic Church. Valid ordination requires that the ordaining prelate traces his episcopate back to the Apostles whom Christ ordained at the Last Supper. Another condition for validity is that the priest or Bishop offering Mass has the intention to do what the Catholic Church understands by consecrating the bread and wine into the living Body and Blood of Christ and offering the sacrifice which Christ made to His heavenly Father by His death on Calvary. Moreover, the priest must pronounce at least the minimum words required for a valid Consecration: “This is My Body,” and “This is My Blood.”
Still another condition for validity is that real bread and wine are used for Consecration, according to the norms set forth in the Code of Canon Law. In the Latin Rite, only unleavened bread is to be used for the Holy Eucharist. In the Eastern Church, leavened bread and unleavened bread are valid matter for the Eucharist. It is, however, illicit to use leavened bread in the Latin Church. At the Ecumenical Council of Florence (1438-1445), it was defined that the Body of Christ becomes really present when the Consecration is made from either leavened or unleavened wheaten bread. The bread must be purely of wheat, and recently made so that there is no danger of decomposition. The wine used must be natural, from the fruit of the grape, pure and incorrupt and not mixed with other substances. It must be stored properly so that it does not turn sour (cf. Redemptionis Sacramentum 48, 50).
In summary, for a valid Holy Sacrifice of the Mass, there must be a valid Consecration. Therefore, it is necessary that a validly ordained priest say the correct words of Consecration, use proper matter, (bread purely of wheat and natural, unadulterated grape wine) and have the intention to do what the Church intends when performing the Consecration. The range of licitness in the offering of the Mass covers the whole spectrum of ritual which the Church prescribes for the offering of the Holy Sacrifice. Two further facts should be noted. Even though a priest is in mortal sin or has abandoned his faith in the Holy Eucharist, the Masses offered by him are still valid, provided the conditions mentioned above are fulfilled. (For Advanced Course lesson 20.)