74 We also want to address with fraternal affection those who belong to the venerable Churches of the East, which have had so many glorious Fathers whose testimony to belief in the Eucharist We have been so glad to cite in this present letter of Ours. Our soul is filled with great joy as We contemplate your belief in the Eucharist, which is ours as well, as we listen to the liturgical prayers you use to celebrate this great mystery, as we behold your Eucharistic devotion, as we read your theological works explaining or defending the doctrine of this most sacred Sacrament.
Source: Mysterium Fidei (Vatican.va)