It is important to note that circumcision and baptism are not always direct parallels, yet it is undeniable that there are several parallels between the two rites. Bill Dejong notes:
It’s obvious how the waters of baptism are a cleansing ritual. The Heidelberg Catechism (in answer 69) compares the waters of baptism to the blood of Christ which washes away our sins. But the “cutting off” of circumcision is also a means of cleansing. That the foreskin was regarded as something unclean is obvious from Paul’s equating of the removal of the foreskin with the “putting off the body of the sins of the flesh” in Colossians 2. The “flesh” is synonymous with foreskin and represents man’s need for cleansing.
Consider in this connection the Israelite leper. The “flesh” of the leper was unclean and could be cleansed in two ways. One, he could be “cut off” (Lev.14), and since the verb here is the same as in Genesis 17, this must be construed as a circumcising process. Two, he could receive a ceremonial cleansing with water, identified in Heb.9:10 as a baptism. The leper thus personifies death and impurity and thus pictures the condition of man in general. The paradigms of cleansing and purification for the leper are circumcision and baptism.