The embolism is not optional.
From the Roman Missal’s Order of Mass:
“With hands extended, the priest continues alone:
Deliver us, Lord from every evil and grant use peace in our day. In your mercy keep us free from sin and protect us from all anxiety as we wait in joyful hope for the coming of our Savior, Jesus Christ.
He joins his hands.”
(Roman Missal, Catholic Book Publishing Co., New York, 1985, page 562.)
If the priest does not do this he is failing to faithfully follow a liturgical book, breaching canon 846 of the Code of Canon Law. This is illegal, illicit and a liturgical abuse. As expressed in the 2004 Instruction Redemptiionis Sacramentum:
“[59.] The reprobated practice by which Priests, Deacons or the faithful here and there alter or vary at will the texts of the Sacred Liturgy that they are charged to pronounce, must cease. For in doing thus, they render the celebration of the Sacred Liturgy unstable, and not infrequently distort the authentic meaning of the Liturgy.”
Sometimes the word “invalid” is used. If the priest has a ceremony without bread and wine then there has not be a consecration of them into the Body and Blood of Christ. The “Mass” is invalid. But failing to say the embolism does not make the Mass invalid.
The priest has some flexibility in some parts of the ceremonies about how he says things. But there are no rubrics allowing him to change the words of the embolism from the approved translation. From the 2002 General Instruction of the Roman Missal (GIRM) approved for the USA, which can be accessed from
romanrite.com/girm.html :
“31. It is also up to the priest, in the exercise of his office of presiding over the gathered assembly, to offer certain explanations that are foreseen in the rite itself.
Where it is indicated in the rubrics, the celebrant is permitted to adapt them somewhat in order that they respond to the understanding of those participating. However, he should always take care to keep to the sense of the text given in the Missal and to express them succinctly. The presiding priest is also to direct the word of God and to impart the final blessing. In addition, he may give the faithful a very brief introduction to the Mass of the day (after the initial Greeting and before the Act of Penitence), to the Liturgy of the Word (before the readings), and to the Eucharistic Prayer (before the Preface), though never during the Eucharistic Prayer itself; he may also make concluding comments to the entire sacred action before the dismissal.”
