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Saying the Mysterium Fidei

Date: May 30, 2021
Author: Fr. Edward McNamara, LC

Answered by Legionary of Christ Father Edward McNamara, professor of liturgy and sacramental theology and director of the Sacerdos Institute at the Pontifical Regina Apostolorum university.

Q: Who says “Mysterium fidei” during Mass, especially when a bishop is the principal celebrant and assisted by several priests? Does a priest take the role of a deacon in announcing “Offerte vobis pacem” and “Ita, missa est”? If the three are roles of a concelebrating priest when a bishop is the president of the liturgy, kindly provide liturgical documents that will help me explain it well to others. -- R.P., Kasama, Zambia

A: In responding to this question, we must distinguish the two situations: the acclamation “Mystery of faith” and the substitution of the deacon by a concelebrant.

In both cases, the most relevant documents are the General Instruction of the Roman Missal (GIRM) and the rubrics themselves. The Ceremonial of Bishops adds some details, but this book usually presumes the presence of the deacon when a bishop celebrates.

The acclamation “Mysterium fidei” was once part of the formula of consecration of the chalice and remains so in the extraordinary form of the Roman rite.

Pope St. Paul VI decided to remove this expression from the consecration. It is not part of the Institution narratives found in the New Testament and may have been added to the missal by Pope St. Leo the Great (A.D. 440-461) to combat the Manichean heresy which rejected the goodness of material things.

Paul VI desired that there be only one form of consecration in all the Eucharistic Prayers, and this required changing the formulation found in the venerable Roman Canon. Thus, in his apostolic constitution promulgating the new missal he wrote:

“As to the words Mysterium fidei, removed from the context of the words of Christ our Lord and spoken by the Priest, these open the way, as it were, to the acclamation of the faithful.”

The GIRM specifies that it is the priest celebrant who proclaims these words:

“151. After the Consecration when the Priest has said, The mystery of faith, the people pronounce the acclamation, using one of the prescribed formulas.”

This is further clarified in the rubrics of all the Eucharistic Prayers. When mentioning the consecration of the chalice it says:

“He [the priest] shows the chalice to the people, places it on the corporal, and genuflects in adoration. Then he says: The mystery of faith.”

The rubrics further specify that this action is done by the celebrant alone.

Furthermore, the Ceremonial of Bishops No. 155 also determines that it is the bishop who says, “The mystery of faith.”

Therefore, we can conclude that, at least in the current Roman Missal, it is always the principal celebrant who intones “Mystery of faith.”

However, it is not an absolute rule. In the closing years of Pope St. John Paul II, and occasionally with Pope Francis, the nearest concelebrant has intoned. Therefore, I would say that, if a celebrant is seriously impeded from singing, another concelebrant could intone the introduction to the acclamation.

With respect to a concelebrant substituting the deacon, the overarching rule is given in GIRM No. 208:

“If a Deacon is not present, the functions proper to him are to be carried out by some of the concelebrants. If other ministers are also absent, their proper parts may be entrusted to other suitable faithful laypeople; otherwise, they are carried out by some of the concelebrants.”

This is a fairly broad principle and can be applied or not in accordance with general principles and the concrete circumstances of the celebration.

One area where it should always be applied is the reading of the Gospel, which should not be proclaimed by the principal celebrant in a concelebration even though he will give the homily afterward. The GIRM says:

“59. The function of proclaiming the readings is by tradition not presidential but ministerial. Therefore the readings are to be read by a reader, but the Gospel by the Deacon or, in his absence, by another Priest. If, however, a Deacon or another Priest is not present, the Priest Celebrant himself should read the Gospel, and moreover, if no other suitable reader is present, the Priest Celebrant should also proclaim the other readings as well. After each reading, whoever reads it pronounces the acclamation, and by means of the reply the assembled people give honor to the Word of God that they have received in faith and with gratitude.”

With respect to the invitation to make the sign of peace, the concelebrant can also substitute the deacon.

“239. After the Deacon or, in the absence of a Deacon, one of the concelebrants, has given the instruction Let us offer each other the sign of peace, all give one another the Sign of Peace. Those concelebrants nearer the principal celebrant receive the Sign of Peace from him before the Deacon does.”

There are two moments when there is no clear indication. The first is the preparation of gifts.

“214. The Preparation of the Gifts (cf. nos. 139-146) is carried out by the principal celebrant, while the other concelebrants remain at their places.”

Although the indication that the concelebrants remain at their places might be interpreted that a concelebrant should not substitute a deacon in preparing the altar, this interpretation is unlikely. GIRM No. 208 does not envisage exceptions, and the origin of the above-mentioned indication to remain until after the Prayer over the Gifts stems from a correction to the first edition of the Rite of Concelebration which foresaw that the concelebrants approach the altar at the beginning of the offertory. This soon revealed itself as a faux pas as the number of ministers around the altar produced an obstacle course during the incensation and other rites of presentation of gifts.

The presence of one concelebrant substituting the deacon does not create any such difficulty and would be especially appropriate when a bishop presides at the celebration.

The second moment is the dismissal at the end of Mass. The GIRM says:

“The Concluding Rites

“250. Everything else until the end of Mass is done by the principal celebrant in the usual way (cf. nos. 166-168), with the other concelebrants remaining at their seats.

“251. Before leaving the altar, the concelebrants make a profound bow to the altar. For his part, the principal celebrant, along with the Deacon, venerates the altar as usual with a kiss.”

Once more, the general principle of GIRM No. 208 would apply, and a concelebrant can substitute the deacon in dismissing the assembly. However, it would not be an obligation and in some cases, it might be easier for the principal celebrant to dismiss the assembly.

If a bishop presides, it would always be preferable for a concelebrant to invite the assembly to bow their heads for the blessing and also to sing the dismissal.

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