God gave Abraham the sign of circumcision in the Old Testament just as He gave the sign of baptism in the New Testament that they might serve as symbols to His people of the inward change that was to take place in their hearts.
Circumcision was a bloody sign to illustrate that apart from the shedding of blood, there is no remission of sin. In contrast, when Christ died as the complete and final sacrifice for sin, there was no longer any need for the shedding of blood. God instituted baptism to give a picture of the washing and regeneration that takes place in the believer’s heart at conversion.
Both these signs have a twofold purpose: