I was baptized as an infant, and I came to understand that I was completely unable to change my attitude towards God (much less His creation) until He graciously intervened and brought me out of the darkness. So I wonder, is it because of some "Covenant" that God made with Abraham, or was it the regenerating work of the Holy Spirit that ultimately brings us to the real kingdom of God? Also, I still cannot find any biblical testimony which would lead me to the conclusion that infant baptism is a necessity, much less an inference. I reread Galatians and the Apostle Paul repeatedly restates that it is not "circumcision" which counts but a renewed and changed heart/life in Christ!
This is worthy a response. So here goes:
First of all, is baptism a necessity? Clearly, Jesus commanded His church to go into all the world and baptize (Matthew 28:18-20). Is obedience to a command of Jesus a 'necessity'? I think so. So the question is really whether infant baptism is included in the command.
To put it another way, however, we might ask whether water baptism is a necessity for salvation. Here we would reply that the sacrament itself saves no one, neither adult nor infant. It is the reality of the cleansing that comes in being joined to Jesus Christ that saves. Thus, we would affirm that not the sacrament of baptism but the baptism in the Holy Spirit is absolutely necessary for salvation for all who would be saved.
It only by grace through faith that we are saved, because all have sinned and fall short of the glory of God. By the original covenant God made with Adam, when he sinned, all his descendants (the whole human race) fell into sin and under condemnation. Infants are children of Adam; they are sinners from the womb. They need salvation like the rest.
Baptism does not save them, but baptism is a sign. This means it signifies something. It signifies cleansing. It signifies the outpouring of the Spirit from heaven. It signifies being joined with Christ.
Baptism is also a seal. This means it confirms something, like a seal placed on a document by a notary public. Baptism confirms the truthfulness of God's promise and the obligation placed upon the members of the church. Church membership saves no one. Water baptism saves no one, neither infants nor adults. But when the members are received into the visible church, they are to be baptized into the name of the Father, the Son, and the Holy Spirit. Their baptism is the rite of initiation which confirms them as members of the church and obliged to obey all that Christ has commanded us, including the commands to repent and believe. Children in the church are to be brought up in the nurture and admonition of the Lord. They are to taught to obey the commandments of Christ. They are to be called to repent and believe. Again, their baptism does not save them, but they are to be pointed to their baptism (infants don't remember the day of their baptism, but they can be reminded of the MEANING of baptism.) They can be reminded that God graciously allowed them to be born of Christian parents, in a Christian home, and to be baptized into a Christian church. Those are great privileges; and they place great responsibility on the child to heed and obey the gospel they are hearing.
So we say again, water baptism does not save anyone, but baptism means something, and it confirms something.
The Reformed faith affirms the continuity of the Old Testament (Old Covenant) and the New Testament (New Covenant). There is only one way of salvation, through faith in Jesus Christ. The old covenant pointed to Christ; the new covenant is the fulfillment of the salvation by Christ. There is a continuity and a fulfillment. The promises made to Abraham are fulfilled in Jesus Christ (specifically, the promised Seed of Abraham would bring blessing to all the nations: see Genesis 12:1-3, 15:5, and chapter 17.). Baptism in the new covenant corresponds to circumcision in the old. The old was a bloody ritual; Jesus' once for all death was the once for all end and fulfillment of the blood sacrifice. The blood of circumcision has given way to the water of baptism, but they mean the same--cleansing; and the true cleansing they represent (signify) is to be found only in the death, resurrection, and ascension of Christ and the outpouring of His Spirit.
To close, here is a quote from the instruction we give from the OPC Directory for the Public Worship of God as it relates to infant baptism:
Although our young children do not yet understand these things, they are nevertheless to be baptized. For the promise of the covenant is made to believers and to their seed, as God declared unto Abraham: "And I will establish my covenant between me and thee and thy seed after thee throughout their generations for an everlasting covenant, to be a God unto thee and to thy seed after thee." In the new dispensation no less than in the old, the seed of the faithful, born within the church, have, by virtue of their birth, interest in the covenant and right to the seal of it and to the outward privileges of the church. For the covenant of grace is the same in substance under both dispensations, and the grace of God for the consolation of believers is even more fully manifested in the new dispensation. Moreover, our Saviour admitted little children into his presence, embracing and blessing them, and saying, "Of such is the kingdom of God." So the children of the covenant are by baptism distinguished from the world and solemnly received into the visible church.
You are absolutely right in saying, "I was completely unable to change my attitude towards God (much less His creation) until He graciously intervened and brought me out of the darkness." And that is precisely what baptism says, "Unless you are cleansed from above by the GRACE of JESUS and by the HOLY SPIRIT you remain in your uncleanness." That is what baptism says to us and to our children, and that is very biblical!
Yours in Christ,