Just a heads-up: the General Introduction to Christian Initiation (GICI) deals nearly exclusively with Baptism. But in this section it does mention the other two initiation sacraments. Let’s read:
2. Baptism incorporates us into Christ and forms us into God’s people. This first sacrament pardons all our sins, rescues us from the power of darkness, and brings us to the dignity of adopted children (Colossians 1:13; Romans 8:15; Galatians 4:5. Also Council of Trent, session 6, Decr. de justificatione, cap. 4), a new creation through water and the Holy Spirit. Hence we are called and are indeed the children of God. (1 John 3:1)
By signing us with the gift of the Spirit, confirmation makes us more completely the image of the Lord and fills us with the Holy Spirit, so that we may bear witness to him before all the world and work to bring the Body of Christ to its fullness as soon as possible. (Ad Gentes 36)
Finally, coming to the table of the eucharist, we eat the flesh and drink the blood of the Son of Man so that we may have eternal life (John 6:55) and show forth the unity of God’s people. By offering ourselves with Christ, we share in the universal sacrifice, that is, the entire community of the redeemed offered to God by their High Priest (Augustine, De civitate Dei 10:6: PL 41, 284, Lumen Gentium 11, Presbyterorum Ordinis 2.), and we pray for a greater outpouring of the Holy Spirit, so that the whole human race may be brought into the unity of God’s family. (Lumen Gentium 28)
Thus the three sacraments of Christian initiation closely combine to bring us, the faithful of Christ, to his full stature and to enable us to carry out the mission of the entire people of God in the Church and in the world. (Lumen Gentium 31)
Scripture provides a good portion of baptismal theology. The apostle Paul wrote significantly on it, and it provides the foundation of our sacramental heritage. Note the use of the word “incorporation,” believers are baptized “into” Christ’s Body. Note the other verbs, strong verbs: form, pardon, rescue, bring to dignity, called.
Confirmation is described as a completion, making the believer the image of Christ. Note: not “into,” but a complete transformation. Confirmation is also linked to the evangelical activity of the Church.
The Eucharist, too, shares this aspect with Confirmation. The Eucharist is also evidence for and celebration of the unity of believers as one sacrifice offered by Christ.
As a unit, these sacraments give us what we need to preach Christ and to be Christ for the world. Note the language: believers are not just a symbol of Christ, but to the world, they are Christ. This “stature” is not for the honor of human beings, either individually or collectively, but has a point, a purpose: the ultimate unity of all humankind under God.