Romans 4:11 And he received the sign of circumcision, a seal of the righteousness of the faith which he had yet being uncircumcised: that he might be the father of all them that believe, though they be not circumcised; that righteousness might be imputed unto them also:
Abraham received the sign of circumcision. This sign, this circumcision would be a type of something later to come. This sign was a seal. It was a seal of the faith. A seal is something that is yet to be opened. Paul is showing us that something for Abraham was yet to come. There is a circumcision coming that his physical circumcision is but a mere picture looking forward to the coming of the real thing. What could that true circumcision be that Paul is talking about?
Colossians 2:11 In whom also ye are circumcised with the circumcision made without hands, in putting off the body of the sins of the flesh by the circumcision of Christ:
The removal of our sins is described in Colossians as a circumcision made without hands. It was the putting away of the sin of the flesh. Just as the foreskin would be removed during physical circumcision, sin would be removed by the circumcision that came by Jesus Christ. This was the true circumcision that was to come. It was the removal of sin via the law of faith. God gave physical circumcision as a type, or a picture of what Christ would come and perform. The Old Testament is a picture of how God would deal with His people in the Lord Jesus Christ. They looked forward to Him, we look back to Him. Abraham looked forward as the father of all who believe to those who would come after him who would have righteousness imputed to their accounts the same as himself. All would have that righteousness imputed at one moment, at the cross of Christ.
Hebrews 11:39 And these all, having obtained a good report through faith, received not the promise: 40 God having provided some better thing for us, that they without us should not be made perfect.
These verses have been used previously. Abraham died not receiving yet the promise that God had made to him. He looked forward to the coming Messiah and all that were in the Messiah would be made perfect not individually, or at separate time, but all at once. All at and by the cross.