Letter 534: Theodore Studite, Letter 534; Greek heading: Συμεὼν μονάζοντι.

The question put forward by your honor ought to have received its clarification from within yourself; for it belongs not to the uninitiated, but to those who are even able to benefit others as well. For "what fellowship," says the Apostle, "has light with darkness, or what portion has a believer with an unbeliever?" [2 Corinthians 6:14-15]. If, then, the cup of blessing is the communion of the blood of Christ, and the bread which we break is the communion of the body of Christ [1 Corinthians 10:16], it is clear that the heretical cup and bread are likewise the communion of the adversary [the devil]. And if these things are so by common confession, it is evident that, in the case of those who have fallen asleep [the deceased] in the one or the other communion, in that same communion they will also have their allotted portion. As for us, we must take care in such cases to make the commemoration [anaphora, the liturgical offering and remembrance of the dead] according to what has been approved, lest we hear, "You ask and do not receive, because you ask wrongly" [James 4:3].