“Now when the apostles at Jerusalem heard that Samaria had accepted the word of God, they sent Peter and John to them. The two went down and prayed for them that they might receive the Holy Spirit (for as yet the Spirit had not come upon any of them; they had only been baptized in the name of the Lord Jesus). Then Peter and John laid their hands on them, and they received the Holy Spirit.”
It is evident from its celebration that the effect of the sacrament of Confirmation is the full outpouring of the Holy Spirit as once was granted to the apostles on the day Pentecost.
From this fact, Confirmation brings an increase and deepening of Baptismal grace:
• It roots us more deeply in the divine filiation which makes us cry “Abba! Father!”;
• It unites us more firmly to Christ;
• It increases the gifts of the Holy Spirit in us;
• It renders our bond with the Church more perfect;
• It gives us a special strength of the Holy Spirit to spread and defend the faith by word and action as true witnesses of Christ, to confess the name of Christ boldly, and never to be ashamed of the Cross.
Catechism of the Catholic Church #1302, #1303