Baptism, we believe, is one of the miraculous means of grace (together with God's written and spoken Word) through which God creates the gift of faith in a person's heart. Although we do not claim to understand how this happens or how it is possible, we believe (because of what the Bible says about baptism) that when an infant is baptized God creates faith in the heart of that infant. This faith cannot yet, of course, be expressed or articulated, yet it is real and present all the same (see, e.g., 1 Pet 3:21; Acts 2:38-39; Titus 3:5-6; Matt. 18:6; Luke 1:15; 2 Tim.3:15; Gal. 3:26-27; Rom. 6:4; Col. 2:11-12; 1 Cor. 12:13).
It’s ironic that some Christians use John the Baptist as a posterboy for infant baptism. According to Lk 1:15, John the Baptist was already in a state of grace in his mother’s womb. If he was sanctified in his mother’s womb, then what would baptism do for him? Are you sanctified before you’re regenerated?
Perhaps, instead of infant baptism, we should practice prenatal baptism by baptizing pregnant women!
Far from being a prooftext for infant baptism or baptismal regeneration, the case of John the Baptist, if it’s even germane to the issue, would be a prooftext to the contrary.