There is one body and one Spirit, just as you were called to the one hope that belongs to your call, one Lord, one faith, one baptism, one God and Father of us all, who is above all and through all and in all.
Catholics don’t believe in justification by works. We know there isn’t anything you can do to earn the initial justifying grace of God. So we baptize babies. Some people take umbrage at this, so much umbrage, in fact, that they insist on rebaptizing you as an adult if you were baptized as an infant. But this is, in the end, to say that a person can only have the grace of God if they are smart enough to know what’s going on in baptism. Catholics know that babies are just as entitled to the grace of God by their braininess as adults are: which is to say, not at all. But God never said He’d give us His grace because we are smart. He said He’d give it to us because He loves us. So we baptize once and trust Him to do the job. All subsequent baptisms just get you wet. God heard the baptismal prayers offered for you the first time.