11 And he received the sign of circumcision, a seal of the righteousness of the faith which he had while still uncircumcised, that he might be the father of all those who believe, though they are uncircumcised, that righteousness might be imputed to them also,
Now we come to the true meaning of Abraham’s circumcision. Verses 11 and 12 set forth two interconnected purposes. Paul separated these two purposes into sections for emphasis. The Jews claimed that they were God’s chosen people and anyone who would have right relation with God must become a proselyte of Judaism.
The purpose of circumcision was as both a “sign” and a “seal.” As a sign it pointed beyond itself to what it represented. As a seal it authenticated righteousness that comes by faith; for example, it authenticated Abraham’s righteous standing in God’s eyes, obtained by faith before he was circumcised. A sign points to God’s promise, but a seal guarantees it.
Gentiles of verse 11 were saved by faith. Abraham was the pattern of how people are saved.
11 And he received the sign [distinguishing mark] of circumcision [cutting off the foreskin of the penis],
The “sign” of circumcision was the seal of Abraham’s justification by faith. This was a symbolic rite of, not the reason for, justification. Circumcision was an outward token of God having declaring him righteous.
Ge 17:11, and you shall be circumcised in the flesh of your foreskins, and it shall be a sign of the covenant [Abrahamic covenant, Ge 12-15] between Me and you.
a seal of the righteousness of the faith which he had while still uncircumcised,
Circumcision of Abraham did not occur until after his justification by faith. God justified him while he was still a Gentile.
A “seal” was the mark of ownership in biblical times, but it was also a means of attestation. The seal was the final ratification, not the preliminary condition of justification. God gave the seal of circumcision to show that He had already executed justification on Abraham’s behalf.
That he might be the father of all those who believe,
Abraham’s justification as a Gentile is the operating principle whereby God justifies all people, both Jew and Gentile. God’s purpose in justifying Abraham while he was a Gentile was that he might be the father of all, both Jews and Gentiles. He did this for the purpose of saving Gentiles!
Though they are uncircumcised,
Uncircumcised Gentiles can be justified by faith, just like Abraham.
that [in order that] righteousness might be imputed to them also,
The second “that” of this verse indicates purpose. God intended to reckon Gentiles righteous by faith. Gentiles receive the privilege of God putting His righteousness to their account by faith.
God personally guarantees us that He will save us eternally.
God gives seals to guarantee the trustworthiness of His promises. Both signs and seals are invaluable. They do not bring about justification but they ratify what is already indicated. We can place our undivided trust in His promises. God puts His own character on the line by guaranteeing our salvation if we trust His word.
Eph 4:30, And do not grieve the Holy Spirit of God, by whom you were sealed for the day of redemption.