So for a good long time, when the priest was saying mass (at least according to the Roman rite), there were rubrics (red letter rules) for even how the fingers were held. The tradition was that the priest would hold the thumb and forefinger together from the time of the consecration until the ablutions. Now, to be sure, this is not so much observed today since most masses are Novus Ordo but this rule is still observed in Latin Mass. This practice comes from the doctrine of the Real Presence and expresses in action what the Church believes about Christ's presence in the Sacrament of the Altar. It may seem rather trivial but it was not meant as something trivial but profound.
Once the consecration takes place and the Word of the Lord is addressed to the elements of bread and wine, then our Lord is really present -- really and truly and substantially present -- in the bread and cup. This is not some vague presence deposited in the faith of the presider or of the communicant or some spiritual presence that has nothing to do with the bread and wine. It means that every crumb of bread and every drop of wine is His body given and shed for the forgiveness of our sins. The crucified and risen Lord is presence among us, on the altar, to be adored, received, and honored with thanksgiving and praise.
As the Rev. Dr. Arthur Carl Piepkorn once put it: And so in the transcendent miracle of the Holy Sacrament we stand in the presence of Calvary's sacrifice, the body that was given for our transgressions and the infinitely precious blood shed for our sins, and plead Christ's mercit for that which we most need and desire. The Rev. Berthold von Schenk put it this way: The handbook of the Church is St. Paul’s first letter to the Corinthians, but we have misunderstood his arguments. ‘Discerning the Body of Christ,’ our exegetes taught concerning 1 Corinthians 11, means ‘believing that the bread is actually the Body of Christ and the wine actually the Blood of Christ.’ This is how they defined the Real Presence. “At Communion we are actually on the mount called Calvary.” Consequently, von Schenk teaches: “In Communion, as nowhere else, the believer is caught up in this
great continual act, this timeless offering of the one sacrifice on the Cross.”
If we believe this and confess it, then how we handle the things of God is not adiaphora or something indifferent. The ancient practice of the priest not casually handling other things after handling the very body of Christ is the practice of the belief in the Real Presence. So when the priest kept those two fingers together except when distributing communion, he was being mindful of that Real Presence and keeping the hands devoted to the one task of distributing the body and blood of Christ until at the end he washed them and the vessels in the ablutions. The simple practice of holding the fingers together was a constant reminder to priest and people of the awesome mystery held in his hand.
We quickly sniff at the superstition of such a practice as if we are above all of that kind of stuff but could it be that the problem is that we no longer believe what the priest's fingers handle is the very body of Christ? Could it be that the lackadaisical way our people treat being in Church on the Lord's Day and preparing for Communion and the way the reliquae (what remains after the Eucharist is complete) are handled are symptoms of a much deeper problem than rubricitis? Could it be that we simply no longer believe that it is the body of Christ and His blood or else we don't believe it matters all that much one way or another?
Practices do not generate belief nor do they, in and of themselves, guarantee orthodoxy but they reflect well what we either do or do not believe. So what do we not believe about the Real Presence when the vessels are treated casually, when spills are walked over as if nothing had happened, when the faithful are not taught how to receive the body and blood, when there is no ablution of the remains in the sacred vessels, or when the reliquae are put in an old Cool Whip container and placed in a cabinet in the sacristy or tossed into the garbage as if they were nothing of value? You tell me?