This article focuses on the signs that God has given to demonstrate and confirm his covenant love: the Sabbath, circumcision and baptism as signs of admission, and the Passover meal, and the Lord’s Supper. The article also discusses how baptism has replaced circumcision, and the Lord’s Supper has replaced Passover (among the other OT feasts).
Infant baptism is rooted in understanding the nature of the covenant God made with Abraham. The covenant promise was spiritual in nature; hence this covenant continued through to the New Testament. Only the sign of the covenant changed from the Old Testament to the New Testament; namely, from circumcision to baptism.
This article is on the topic of infant baptism. The author discusses the history of the Abrahamic covenant which had the sign of circumcision. With the coming of Christ, this sign of circumcision was replaced by baptism. Infants of believing parents are part of this covenant, and should therefore receive the sign of baptism.