The Sanctus is the prayer of angels and we are privileged to join in their song. Heaven and earth are—indeed—full of God's glory. And at this point in the Mass, we are but moments away from when heaven reaches down and touches earth in the form of the Eucharist, the Body and Blood, Soul and Divinity of Jesus Christ.
Similarly, the rest of the Sanctus is biblically based. As we have been accustomed, it quotes the accolades of the crowds worshipping Jesus as He entered triumphantly into Jerusalem. On Palm Sunday, the crowds welcomed Jesus into their midst with shouts and cries of "Hosanna!" (See Mt. 21:9) They also sang praises that echoed Psalm 118: 26: "Blessed is he who comes in the name of the Lord."
'Hosanna' is a transliteration of a Hebrew word meaning "Save us," which became an expression of praise in liturgical worship. The blessing upon "he who comes in the name of the Lord," was normally invoked on the pilgrims coming into the Temple. On the day we know as Palm Sunday, the crowds used these words to welcome Jesus as the one coming in the Lord's name—in other words, the one representing God and acting on his behalf.
It is fitting that we repeat these words at this moment in the Liturgy. Just as the crowds welcome Jesus into the holy city with these words from Psalm 118, so do we welcome Jesus into our churches, for he is about to become present in the Eucharist on our altars. (Edward Sri, A Biblical Walk Through The Mass, Ascension Press, 2011, p.104)
The Mystery of Faith (formerly known as "The Memorial Acclamation")
There are four acclamations currently in use, but soon there will be three. Of the three that will remain, nominal changes will come to each.
This is the current translation.
Priest: Let us proclaim the mystery of faith.
A) Christ has died, Christ is risen, Christ will come again.
B) Dying you destroyed our death, rising you restored our life. Lord Jesus, come in glory.
C) When we eat this break and drink this cup, we proclaim your death, Lord Jesus, until you come in glory.
D) Lord, by your cross and resurrection you have set us free. You are the Savior of the world.
The new translations will read as follows.
Priest: The mystery of faith.
A) We proclaim your death, O Lord, and profess your Resurrection until you come again.
B) When we eat this Bread and drink this Cup, we proclaim your death, O Lord, until you come again.
C) Save us, Savior of the world, for by your Cross and Resurrection, you have set us free.
The Mystery of Faith follows the consecration of the Eucharist. This is a moment of wonder and awe for both priest and people. The Mystery of Faith describes that profound understanding of the magnitude of Christ's gift to us in the Eucharist, and our acclamation ought to suitably express deep gratitude. The three acclamations in the New Missal suitably fit this intention.
Certainly we also notice that the first acclamation is no longer listed. The United States Catholic Conference of Bishops' website offers two reasons for its removal.
What is conspicuously absent is the popular current acclamation, "Christ has died, Christ is risen, Christ will come again." This line, although powerful, is not found in the Latin. In addition, unlike the other acclamations, it does not directly address Christ made present in the Blessed Sacrament, nor does it speak of our relationship with Him. (USCCB, Commentary on the Mystery of Faith)
These remaining three acclamations are found in the Latin translation that the new English translation is based upon. They are rooted in the New Testament.
Options A and B recall 1 Corinthians 11: 26: "For as often as you eat this bread and drink the cup, you proclaim the death of the Lord until he comes."
Option C is found in a portion of John 4:42. It echoes the Samaritan's woman's faith: "we know that this is truly the savior of the world."
The revised Roman Missal, third edition, will more perfectly follow its Latin predecessor that appeared in 2002. This is the first major change to the English Mass texts since 1973. For some younger Catholics, this is first ever change that they have experienced.