Calvin emphasized several key themes in his treatment of baptism in this edition of the Institutes: witness to divine promises; Jesus Christ as substance and foundation; connection between circumcision and baptism; covenant; and election. Calvin would further develop, clarify, and deepen these themes when dealing with baptism for the next two decades. In so doing, however, he did not depart in essential ways from the themes dealt with in this chapter.
Witness to divine promises
In this chapter, Calvin brought into bold relief the claim that baptism bears witness to God's promises concerning forgiveness of sins, mortification of the sinful nature, new life, and hope for the future. The water itself does not bring any of these things about; rather, it points to the salvation made possible in the death and resurrection of Jesus Christ from the dead. Baptism bear witness also to the ongoing effect of divine grace in the lives of the baptized. With echoes of Luther, Calvin proclaimed:
…We must know that, whenever it is that we are baptized, we are washed and purified once for the whole of our life. That is why every time we fall into sin again we must return to the memory of our baptism, and by that confirm ourselves in the faith that we are always certain and assured of the remission of our sins. For even if, since it was once administered, our baptism seems to us already past, nevertheless, it is not wiped out by subsequent sins. For Jesus Christ's purity is offered to us in baptism, and it always has its force; it endures forever and cannot be overcome by any stain but abolishes and cleans all our stains and impurities.
Baptism functions as a kind of perpetual witness to the baptized of the perpetual grace of God made known in Jesus Christ. Baptism cannot be repeated because the once and for all death of Jesus Christ for our sins to which it points is both a singular event and something that remains perpetually in effect. Baptism reminds the baptized of the all-sufficient and continually available grace of forgiveness through the crucifixion. Though with Zwingli Calvin also affirmed that baptism functions as a public witness concerning the primary allegiance of the baptized, that theme is underdeveloped in this edition of the Institutes and is overshadowed by the intra-ecclesial and pastoral function of baptism.
Jesus Christ as substance and foundation
Drawing deeply from the liturgical theology of St. Augustine, Calvin affirmed that Jesus Christ is the substance and foundation of baptism. It is the shed blood of Jesus Christ on the cross that brings about our salvation and our reconciliation with God—not the sanctified element of water in and of itself. Further, the risen and ascended Jesus Christ continues to act in salvation and regeneration. Though pastors administer the sacrament, it is really, "Jesus Christ [who] is the author of the inward grace." Even though baptism has an unmistakable christological focus and it is to union with Jesus Christ that baptism points, in actuality the whole Trinity acts in baptism:
For all God's gifts that are offered in baptism are found in Christ alone. Nevertheless it is not possible for one who baptizes in Christ's name not to invoke likewise the name of the Father and of the Son and of the Holy Spirit, for the reason we have our purification in Christ's blood is because the Father, wanting to pour out His goodness and mercy, reconciled us to Himself by Him. Then we obtain regeneration in His death and His life if, by the sanctification of the Spirit, there is a new spiritual nature built up in us. That is why the cause of our purification as well as our regeneration ought to be recognized to be in God the Father, the ground of matter of it in the Son, and the efficacy in the Holy Spirit.
Calvin's treatment of baptism in this chapter has a deep, practical christological character set within the larger context of a dynamic trinitarian framework.
Connection between circumcision and baptism (and paradigm for Christian living)
Taking biblical cues from Paul's letter to the Colossians and the institution of circumcision with Abraham in Genesis 17, Calvin provided extended exegetical and theological reflections on the close interconnection between the two rites in the heart of this chapter. Though there are some important differences between the two, Calvin forcefully maintained that, "…We always keep the likeness which remains between baptism and circumcision regarding the interior mystery, the promises, the use, and the efficacy." They may differ in externals, but the inner meaning is exactly the same. This close identification of circumcision and baptism provides the key that unlocks Calvin's understanding of the necessity of infant baptism.
Just as the children of the Israelites were initiated into the community through circumcision on their eighth day of life, so the babies and young children of Christian parents should be initiated into the church through baptism as early as possible. In both instances, understanding and faith come later and, at least partially, as the result of the conditions created by the fact of initiation into the community of faith. To strengthen his case for infant baptism, he invoked the command of Jesus in Matthew 19 to allow little children to come to him. He also called upon the Old Testament promise quoted by Peter on the day of Pentecost to the effect that the promise of divine grace is for believers and their children.
The deeper bond between circumcision and baptism can be found in the biblical concept of covenant. The community of faith called into being by God is bound to God, to one another, and to a particular pattern of life. For the ancient Israelites, that distinctive pattern of life was defined by the Torah or the Law; for Christian churches baptism serves as the parallel. Speaking to the pattern of regeneration that should issue forth in the life of baptized children—should they live long enough to reach the age of instruction—Calvin held that they should be taught so that, "They will recognize how in all their life they should do nothing else than meditate on and practice this regeneration of which they bear the mark from their childhood." In other words, baptism provides the paradigm for the entirety of the Christian life. The covenantal community of the baptized is marked by daily dying and rising with Christ—which Calvin in other places referred to as "mortification" and "vivification." In this, Calvin simply yet profoundly brought out the meaning of Paul's teaching about the implications of baptism for the Christian life in Romans 6.
The doctrine of election provided the foundation for all of Calvin's teaching about baptism. The salvation to which baptism functions as sign and witness depends solely upon God's choice and action, not on human initiative. Calvin put a fine point on this teaching when speaking of baptized infants who die:
Children who receive the sign of regeneration and renewal, and who die in this world before coming to the age of understanding, if they are the Lord's elect they are regenerated and renewed by His Spirit as He pleases according to His power which is hidden form us and incomprehensible to us.
In this teaching, Calvin was merely working out the logical and necessary implications of his conclusions about what the Bible has to say about divine election in a more general sense. The issue of election and baptized children would require further development and nuance by Calvin in the years following this edition of the Institutes. The core affirmation, however, of divine initiative and prerogative remained constant in his reflections on both election and the ultimate status of the baptized who die in infancy.