Heidelberg Catechism 26.74

Chapter 26 — Lord's Day 26

Section 74. Q. 74: Should infants also be baptized? A. Yes. Infants as well as adults are in God's covenant and are his people. They, no less than adults, are promised the forgiveness of sin through Christ's blood and the Holy Spirit who produces faith. Therefore, by baptism, the mark of the covenant, infants should be received into the Christian church and should be distinguished from the children of unbelievers. This was done in the Old Testament by circumcision, which was replaced in the New Testament by baptism.