There is a famous story from the life of Saint Philip Neri that helps answer that question. One day while he was celebrating Mass, a man received Holy Communion and left the church early. The man appeared to have no regard for the Presence within him and so Philip Neri decided to use this opportunity as a teaching moment. He sent two altar boys with lighted candles to follow the man outside of the church. After a while walking through the streets of Rome, the man turned around to see the altar boys still following him. Confused, the man returned to the church and asked Philip Neri why he sent the altar boys. Saint Philip Neri responded by saying, “We have to pay proper respect to Our Lord, Whom you are carrying away with you. Since you neglect to adore Him, I sent two acolytes to take your place.” The man was stunned by the response and resolved to be more aware of God’s presence in the future.
The Catholic Church professes that, in the celebration of the Eucharist, bread and wine become the Body and Blood of Jesus Christ through the power of the Holy Spirit and the instrumentality of the priest. Jesus said: “I am the living bread that came down from heaven; whoever eats this bread will live forever; and the bread that I will give is my flesh for the life of the world. . . . For my flesh is true food, and my blood is true drink” (Jn 6:51-55). The whole Christ is truly present, body, blood, soul, and divinity, under the appearances of bread and wine—the glorified Christ who rose from the dead after dying for our sins. This is what the Church means when she speaks of the “Real Presence” of Christ in the Eucharist. This presence of Christ in the Eucharist is called “real” not to exclude other types of his presence as if they could not be understood as real (cf. Catechism, no. 1374). The risen Christ is present to his Church in many ways, but most especially through the sacrament of his Body and Blood.
Pope John Paul II reminds us: “The Eucharistic Sacrifice makes present not only the mystery of the Saviour’s passion and death, but also the mystery of the resurrection which crowned his sacrifice”. Christ can only become the Bread of Life for us because He is risen from the dead and is alive for us in the Church. We refer to the living presence of Christ with us in the Holy Eucharist as the Real Presence.
St. Ambrose said: “If the word of the Lord Jesus is so powerful as to bring into existence things which were not, then a fortiori those things which already exist can be changed into something else” (De Sacramentis, IV, 5-16).
The great treasure of the Catholic Church is the Eucharist — Jesus himself hidden under the appearances of bread and wine. We believe, as the Catechism states, that “In the most blessed sacrament of the Eucharist ‘the body and blood, together with the soul and divinity, of our Lord Jesus Christ and, therefore, the whole Christ is truly, really, and substantially contained'” (CCC 1374).
Additionally, this Real Presence of Christ in the Eucharist does not end immediately when we receive him at Communion time. The Catechism goes on to explain how, “The Eucharistic presence of Christ begins at the moment of the consecration and endures as long as the Eucharistic species subsist” (CCC 1377).
What does that mean when we receive him into our mouths? How long does Jesus’ Real Presence remain in our bodies?
It is generally assumed that the Eucharistic species of bread remains for about 15 minutes after reception. This is based on simple biology and reflects the Catechism’s statement that the presence of Christ “endures as long as the Eucharistic species subsist.”
This is why many saints have recommended offering 15 minutes of prayer after receiving the Eucharist as a thanksgiving to God. This allows the soul to savor the presence of God and have a true “heart-to-heart” with Jesus.
In our face paced world it is often difficult to remain long after Mass, but that doesn’t mean we can’t at least pray a brief prayer of thanksgiving. The main point is that we need to remember Jesus’ presence in the Eucharist stays with us for several minutes and presents us with a special time when we can commune with our Lord and feel his love within us.
If one day you forget, don’t be surprised if your parish priest sends altar servers to follow you to your car when you leave Mass early!