“Behold, I stand at the door and knock; if anyone hears My voice and opens the door, I will come in to him and eat with him, and he with Me... After this I looked, and lo, in heaven an open door…”
Revelation 3:20, 4:1
We go to heaven when we go to Mass. This is not merely a symbol, not a metaphor, not a parable, not a figure of speech. It is real…We do go to heaven when we go to every Mass and is true of every Mass we attend, regardless of the quality of the music or the fervor of the preaching…The Mass-and I mean every single Mass-is heaven on earth.
Scott Hahn, Lamb’s Supper
When Christ becomes present in the Eucharist He is in heaven, without leaving heaven, that means heaven is present with him ... Christ doesn’t leave heaven to be present in the Eucharist, and his presence in the Eucharist is not different from his presence in heaven. There are many consecrated Hosts throughout the world, but Christ doesn’t multiply Himself to be present in all those different places. There is only one Christ, one presence of Christ….
7 Secrets of the Eucharist, pp 26-27
The Church knows that the Lord comes even now in his Eucharist and that he is there in our midst. However, his presence is veiled. Therefore we celebrate the Eucharist "awaiting the blessed hope and the coming of our Savior, Jesus Christ," asking "to share in your glory when every tear will be wiped away. On that day we shall see you, our God, as you are. We shall become like you and praise you forever through Christ our Lord.
Catechism of the Catholic Church, #1404
The whole Christian life is a communion with each of the Divine persons, without in any way separating them… We are called to be a dwelling for the Most Holy Trinity. “If a man loves me… my Father with love him , and we will come to him and make our dwelling with him” (John 14:23)
Catechism of the Catholic Church #259, 26
Where the Father and the Son are present, the Holy Spirit is also there*. Whenever we receive Communion we enter into communion with the Holy Trinity. The Blessed Trinity dwells in the heart of each person who receives the Eucharist.
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*Each person of the Trinity is consubstantial with the others (The Father, Son and Holy spirit are of the same divine nature or substance)
We believe that that the Father, Son, and Holy Spirit are each present in each other without ceasing to be distinct (circumincession)
See 7 Secrets of the Eucharist pp 29 - 31 for a deeper understanding.