Just as Baptism gives new life, Eucharist nourishes life, and Reconciliation restores life when it is broken, Confirmation strengthens that life by the gifts of the Holy Spirit (cf. CCC 1285). It is about strengthening what God has given, and continues to give, to his sons and daughters (cf. CCC 1302-1303).
Confirmation is not a “coming of age” celebration. True, most young people are just beginning to pass into early adulthood when they receive the sacrament. But Confirmation is not about coming of age. Reception of the Sacrament of Confirmation does not mark the end of formal religious education. We never outgrow a need for a deeper knowledge and appreciation of our faith.
The Sacrament of Confirmation is not a rite of passage, nor a graduation from religion class, nor a ratification of a personal faith choice. Rather, it’s all about what God is doing for his beloved daughters and sons.
And what is God doing? Strengthening the divine life which he gave at Baptism, nourishing us in the Eucharist, and reconciling with us in Penance. Why? So that the individual can better defend and witness to the faith through the gifts and workings of the Holy Spirit. And there are—and will be—many situations where we are called upon to defend and witness to our faith. And we need all the help we can get!
A part of the theology of the sacrament is that one takes on more adult responsibilities for the faith and becomes a “soldier for Christ” when confirmed. Any good soldier must be willing to suffer the bruises and scars of battle. The slap on the cheek was a symbolic gesture intended to remind us of the fact that we may have to endure suffering for our faith. The Sacrament of Confirmation strengthens us making us willing to accept those responsibilities and, if necessary, suffer and die for the faith.
In the Sacrament of Confirmation, the Holy Spirit completes the grace of baptism and offers the newly confirmed strength as a true witness of Christ. Thus, the newly confirmed is “more strictly obliged to spread and defend the faith by word and deed” (cf. CCC, 1285). Thus, the Holy Spirit completes what was begun at baptism.