3. The Command of the Church.
The Church teaches that we must fulfill the command of Jesus (“Do this in memory of me”) by attending Sunday Mass (or the Vigil Mass the night before). The Catechism of the Catholic Church (1994, pp. 493-94) explains that Mass attendance on Sundays and Holy Days of Obligation is the first of the six Commandments of the Church. These Commandments of the Church also require receiving Communion at least once a year during the Easter season, confessing any mortal sin as a preparation for Communion, and observing the prescribed days of fasting and abstinence. These Commandments spell out the minimal responsibilities of a Catholic. To fail to fulfill them through our own fault, the Church teaches, is a serious sin.
4. The Church speaks with the authority of Jesus.
Why should we obey these teachings of the Church? Where does the Church get its authority? From Jesus. In Matthew 16:18-19, Jesus made Peter the head of his Church — the first Pope. He gave Peter and the Church “the keys to the kingdom of heaven”:
I say to you, you are Peter, and upon this rock I will build my church, and the gates of hell shall not prevail against it. I will give you the keys to the kingdom of heaven. Whatever you bind on earth shall be bound in heaven; and whatever you loose on earth shall be loosed in heaven.
The Church’s authority in faith and morals is absolute because Christ’s authority is absolute.
5. What we do at Mass.
The Mass is first of all a sacrifice — the perfect sacrifice, created by Jesus. Through the priest we offer Jesus, Body and Blood, to the Father, just as Jesus offered Himself to the Father on the Cross. In an unbloody way, we repeat — make present — Christ’s death and Resurrection. Through this memorial of Jesus, we offer God our praise, sorrow for our sins, and deepest thanks.
The Mass is also a meal. At the Consecration, the bread and wine, through the power of the Holy Spirit, become the Body and Blood of Christ. Not a mere symbol, but Jesus’s real flesh and real blood, under the appearance of bread and wine. When we receive Holy Communion, we receive Jesus Himself. He is real food for our soul. He said this very plainly: I say to you, unless you eat the flesh of the Son of Man and drink his blood, you do not have life within you. Whoever eats my flesh and drinks my blood has eternal life, and I will raise him on the last day. My flesh is true food, and my blood is true drink. Whoever eats my flesh and drinks my blood remains in me and I in him. (John 6:55-56).
What are the benefits of Holy Communion? It strengthens our union with Jesus; He lives within us in a special way. It cleanses us from venial sins. (Mortal sins require forgiveness in Confession.) It gives us grace to avoid sin in the future. It increases our love of God and neighbor.