Then who does the Holy Spirit come to? What exactly is the Catholic teaching?
The Church teaches what the Scriptures say: While God is not limited to the Sacraments, they are the ordinary way we receive the greatest gifts of the Holy Spirit. If you read Acts 8, you’ll see that certain people were “saved” (1 Pet. 3:21) by being baptized, however, they had not yet “received the Holy Spirit”. That is because these are two different Sacraments, and the second, the Sacrament of Confirmation can only be conferred by an Apostolic authority - a bishop*.
Your problem is you’re trying to make the exception the rule, even though you see that the Apostle, St. Peter, was “astonished” because God had circumvented the ordinary means of receiving these gifts, which He had taught them.
- A bishop can grant a dispensation for a priest to confer Confirmation; just as, by exception, any baptized Christian can baptize, although it ordinarily must be done by an ordained priest or deacon, like Philip (Acts 5:5-6).
According to Paul, believers receive the Holy Spirit upon belief:
Once again, you’re taking scriptures out of context from the rest of Scripture…
“Whoever believes and is baptized will be saved” (Mark 16:16)
“Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit." (Acts 2:38)
“When they arrived, they prayed for the new believers there that they might receive the Holy Spirit, because the Holy Spirit had not yet come on any of them; they had simply been baptized in the name of the Lord Jesus. Then Peter and John placed their hands on them, and they received the Holy Spirit.” (Acts 8:15-17)
These are the ordinary steps for sinners to convert: believe, repent, Baptism, Confirmation. Those who have not sinned, because they have not reached the age of reason, can “immediately” receive the free gift of salvation in Baptism, based on the faith of their parents (Acts 16:33).
Also according to Paul, having the Holy Spirit is a sign of belonging to God:
Correct…
So in accordance with what Paul says in Ephesians and Romans, Cornelius believed the gospel, received the Holy Spirit (which is evidence of salvation), and was then baptized. If he had the Holy Spirit and therefore belonged to God before baptism, what exactly did the baptism effect?
First, yes, Cornelius clearly had received the Holy Spirit, and so his soul must have already been washed clean, as we already see in the Scriptures with the Blessed Virgin Mary, whose soul was
created pure, and others. So why did St. Peter baptize him? Because there was still something missing: “the mark of Christ”, as you already quoted (Eph. 1:13). The Church teaches that Baptism leaves an “indelible mark” of our Lord Jesus Christ on the soul, which is why the Sacrament of Baptism cannot be repeated.
Don’t worry, the Catholic Church has studied the Sacred Scriptures for 2000 years and harmonized them in Truth, with the help of the oral Apostolic Tradition as well as the Holy Spirit. Which is why She knows that Baptism is not merely symbolic, it saves us. Because, in His infinite wisdom, “God chose the foolish things of the world to shame the wise” (1 Cor. 1:27), like literally washing our souls with the waters of the Holy Spirit. So stop leaning on your own faulty understanding; put your trust in the Lord, who gave you His Catholic Church, the pillar and foundation of the truth, against which the gates of Hell will not prevail. And you can see for yourself, after 2000 years, the successor of Peter, to whom Our Lord made the promise, Pope Benedict XVI is right there in Rome, where Peter died a glorious martyrs’ death, shepherding the People of God, proving Our Lord keeps His promises. God bless.