On this Trinity Sunday, it is good to reflect on the relationship between the Eucharist and the Trinity. Vinny Flynn does a very good job of this in his book, 7 Secrets of the Eucharist. He starts off Chapter 2, "Christ is not Alone," with a quotation from St. Faustina's Diary:
Jesus... You come to me in Holy Communion, You who together with the Father and the Holy Spirit have deigned to dwell in the little heaven of my heart. (486, quoted in Flynn, p. 19)
As Flynn discusses later in the chapter:
Christ is the second person of the Blessed Trinity, true God and true man eternally united with the Father and the Holy Spirit. Just as there can be no separation within Christ's human nature, so there can be none within His divine nature. Just as we cannot separate Christ's body from His blood, or His soul from His body and blood, so we cannot separate Christ from the other persons of the Trinity. (p. 25)
Flynn goes on to say:
With each reception of Holy Communion, we experience, already here on earth, the same divine activity that we will one day experience in all its fullness in heaven - the divine activity of love eternally taking place within the Trinity. (p. 27)
As Flynn notes, only Christ is sacramentally present in the Eucharist, but all of the Trinity is really and truly present (p. 29). Flynn goes into the theology of this paradox, followed by some wonderful entries from St. Faustina's Diary. All important reflections on this Trinity Sunday that help us to understand better some of the many dimensions of the Eucharist.