That’s how Taylor Marshall describes it, discussing that topic over on his blog.
The Catholic Church has traditionally seen deacons as necessarily chaste and continent because they touch the sacred chalice. I would like to argue that the sacred chalice is itself “the mystery of faith” and this has become forgotten in modern liturgics.
One difficulty in the post-Vatican 2 liturgy, now recognized by many liturgists, was the divorce of the “mysterium fidei” from the words of consecration in the missal of His Holiness Pope Paul VI. Prior to 1970, the consecration of the chalice was as such:
Hic est enim calix sanguinis mei,
novi et aeterni testamenti:
qui pro vobis et pro multis effundetur
in remissionem peccatorum.
This is the chalice of my Blood
of the New and Eternal Testament
the Mystery of Faith
which is poured out for you and for many
for the remission of sins.
The place of “mysterium fidei” in the consecration of the chalice goes back to the 600s at least. Saint Thomas Aquinas taught that the words “mysterium fidei” should be preserved in the consecration of the chalice, just after the word “testimenti” (cf. STh III, q. 78, a. 3; Super I Cor, c. 11, v. 25).
By the way, nobody here (especially not I) claims that the consecration is invalid without “mysterium fidei.” Of course, all Novus Ordo Masses are valid. Eastern Eucharists are also valid, even though they also lack what the words “mystery of faith” or τὸ μυστήριον τῆς πίστεως. We’re just talking about liturgy and tradition here, not sacramental validity.
The phrase “mystery of faith” was not supposed to be an opportunity to recite an affirmation of the Faith (e.g. “Christ has died, Christ is risen, Christ will come again.”)
Previously, the “mystery of faith” is the chalice of the Precious Blood itself which is the New and Everlasting Covenant of Christ. It’s the Blood of Christ in particular that is our “mystery of faith” – not words that we recite.
Notably, the only time the phrase “mystery of faith” (Vulgate: mysterium fidei, Greek: τὸ μυστήριον τῆς πίστεως) appears in the pages of Sacred Scripture is at 1 Timothy 3:8-9:
“Deacons in like manner: chaste, not double tongued, not given to much wine, not greedy of filthy lucre: Holding the Mystery of Faith in a pure conscience.”
Deacons in all rites and traditions, East and West, are associated with the chalice in the liturgy. Deacons literally “hold the Mystery of Faith” at the minor elevation of the Holy Mass. Whether or not Saint Paul intended to denote the Eucharistic chalice by the words “mystery of faith” in 1 Tim 3:8-9, I suspect that the subsequent tradition had a gut feeling that deacons, the mystery of faith, and the chalice go together as an intact unity.