Fundamentalists believe that baptism is only a symbolic washing signifying that a person has accepted Jesus as his Lord and Savior. According to them, since an infant cannot accept Jesus as Lord and Savior (because he does not have the use of reason), baptism is meaningless for him.
However, Jesus requires baptism for entering heaven (Jn 3:5; Mk 16:16). St. Paul tells us that all are born with Adam's sin and thus need baptism (Rom 5:18-19). Jesus makes clear that children are not to be kept away from Him (Mk 10:14). The Apostles baptized entire households (Acts 16:15, 33; 1 Cor 1:16). This would include infants. No bible passage prohibits infant baptism.
The early Church Fathers were clear that the baptizing of infants was a practice that came from the Apostles themselves. That infants lack the use of reason does not prevent them from becoming part of the New Covenant through baptism. In the OT, a child became part of the Old Covenant through circumcision. This was done eight days after birth, long before the child could choose for himself whether or not to be part of the Chosen People. Just as parents in the OT supplied the decision for the child's circumcision until he could confirm this decision at the age of reason, so in the NT parents stand in for the child at his baptism until he can confirm this decision at the age of reason. ✝🔥