Infant baptism is paedobaptism and adult believer's baptistism is credobaptism. In the former the participant has no say in the matter and in the latter, the person makes a choice based on belief.
Among the reasons for paedobaptism is that the infant is believed to be possessed and an exorcism must be done. There is no biblical evidence that early Christians ever practiced infant baptism. There is no doctrine which allows it. All baptisms in the Holy Bible were for believers. Baptism is not for unbelievers... never! Even those of restored faiths still require faith in Jesus Christ to be baptized, and baptism, for them, is the end of the born-again process, but that's not on the table right now for discussion.
One of the reasons for paedobaptism is that it's the New Testament parallel to Old Testament circumcision, and indeed, infants of eight days old were circumcised as part of the Abrahamic Covenant. The "cutting off of the flesh" sealed the deal with God!
However, it was faith which saved Abraham. Even New Testament scripture validates that. Circumcision of adults was for two reasons: 1) a pledge to obey God and 2) and obvious health benefit such that God could fulfill his promise to bless the seed of Abraham. (He couldn't populate the earth with his seed if they were all dying off, could he?)
On the other hand, infant circumcision was a pledge to bring the child up under the covenant. When a baby is dedicated in the church, in contrast to infant baptism, that fulfills the pledge likewise. The infants enjoy the same health benefits as the adults. Therefore, circumcision is not the equivalent of baptism and as such is not a copy. Each are discreet ordinances for each particular covenant time: the law vs. grace. In other words, circumcision is merely symbolic of baptism, but they are not the same. Therefore, assuming infants can be baptized because infants were circumcised as adding to scripture, which we are not to do!
Early Christians and catholics believed that infants, having original sin, are born with evil spirits in their souls. Again, that is not scriptural! We all are born with a propensity to sin, but are born with an empty soul. Only those who can consider their spiritual condition, those of the time of accountability, have anything in their souls at all! We all, even in childhood, do evil, but there an evil spirit is not within unless the person blasphemes the Holy Spirit. As such babies are not possessed and there is no need to exorcize them!
On the other hand, as more mature children begin to sin, the disease of sin accumulates in their soul and it must be washed clean. The blood of Jesus is what does the washing, and baptism with water testifies to that. Baptism seals the deal, so to speak.
Sin can be in the soul even though an evil spirit is not. However, before the Holy Ghost fills the soul, the blood must cleanse the sin within. God cannot look upon sin. Actually, Christians can never be filled with the Holy Spirit because sin still exists. A better interpretation is being imbued with the Holy Spirit. Our spiritual sponge gets cleansed with blood and God's spirit is soaked up, but because of our original condition, sin still takes a portion of the soul preventing it form being entirely saturated.
Entire Sanctification can be strived for, but never obtained. Our soul will always be tainted with some sin and when we think we're clean, we become proud. Our pride disputes what we claim!
Why write this? Because some who claim paedobaptism misunderstand. They were merely wet infants who their parents dedicated to God, but salvation is by faith and only those with faith can be scripturally baptized. In other words only believers; hence credobaptism.
Paedobaptism stands in the way of credobaptism. Misunderstanding surely won't damn the person, but baptism must be done correctly or it has no meaning. Even if one was baptized (sic) as an infant, believer's baptism can still be performed. Anabaptists are those who have been re-baptized. I have been myself.
We are to be baptized when we are convinced that Jesus is the only way to salvation, and allow him to lead our lives. Baptism is an expression of a willingness to change, and those who are born-again can change! In essence, change is the assurance of salvation because we can't serve two masters. We must choose! Baptism is choosing our master.