Genesis 17:9-11 meaning

Since this is now a covenant between Me and you that requires Abraham's participation, God now calls upon Abraham to observe his covenant obligation (Exodus 23:15; Deuteronomy 28:9). This is unlike the previous provision of the covenant, where God passed through the animal halves by Himself, because He was making unilateral promises (Genesis15:10-18). In this case, this is a mutual agreement, and Abram and his descendants have a continuing obligation in order to receive the reward or blessings.    Abram's covenant obligation is specified in verse 10: Now as for you, you shall keep My covenant. God institutes a physical sign of the covenant, namely circumcision. This indicated one's total commitment to God and His covenant. The obligation of the covenant involved the practice of keeping the covenant's sign. This was, in a way, Abram's "signature" on the contract with God, that he would keep his part of the "deal" by being an obedient vassal, or servant, to his superior or suzerain. 

The covenant was God's, and it involved "every male." Specifically, Abraham, every male among you, and your descendants after you were to be circumcised. The institution of circumcision was given as a seal of the covenant. The fact that it applied to all of Abram's descendants emphasized that this covenant would pass down to all of Abram's seed. Circumcision signified a commitment to obey God, that God alone would be worshipped; a commitment to trust and serve God. 

You shall be circumcised in the flesh of your foreskin, circumcision is the removal of the male foreskin. The word circumcision means "to cut around." God chose circumcision as the sign of the covenant between Me and you. It showed physically and tangibly that obedience was necessary to receive additional blessing. However, it did not affect the unconditional promises God had already made. Paul will make a major point of this in his arguments in Romans, noting that Abraham was declared righteous in the sight of God (Genesis 15:6) long before he was circumcised (Romans 4:1-13). It is also worth noting that all these grants and promises, both conditional as well as unconditional, are made many years before God will grant the Law. Paul also makes this point, that God gave the Law "four hundred and thirty years later" (Gal 3:17) because of "transgressions" (Gal 3:19). Apparently Abraham's descendants needed some help discerning what it meant to be blameless in order to receive God's added blessings. 

Circumcision identified Abraham and his descendants as God's own people and reminded them to live in faithfulness to the covenant. The act of circumcision was a confirmation symbol of separation from the world, of holiness, and loyalty to the covenant; it was an act of faith. It is an outer metaphor of the "circumcision of the heart," which means inwardly that one is committed to God, and set apart to God rather than being stubbornly resistant (Leviticus 26:41; Deuteronomy 30:6; Romans 2:28-29, 4:11; Ephesians 2:11). 

When Jesus established the New Covenant, he fulfilled the requirements of the Old Covenant. Therefore, it is not necessary for any believers to be physically circumcised. The Jerusalem Council and the subsequent writings of Paul made this point explicit for New Testament Gentile believers  (Acts 15:1-29; Romans 2:25-29; Galatians 2:1-10, 6:15; Colossians 2:11-12). All believers are placed into God's family through simply believing God's promise in Jesus, without further condition, including any physical ceremony. 

Jewish believers continued to practice circumcision as a cultural expression. Paul had Timothy circumcised (Acts 16:3). Paul also made it clear that he still followed Jewish customs. In Rome, Paul proclaimed to "the leading men of the Jews" that "Brethren, though I had done nothing against our people or the customs of our fathers, yet I was delivered as a prisoner from Jerusalem into the hands of the Romans" (Acts 28:17). He further asserted that he was "forced to appeal to Caesar, not that I had any accusation against my nation" (Acts 28:19). He further asserts to the Jewish leaders in Rome that "I am wearing this chain for the sake of the hope of Israel" (Acts 28:20). Paul's assertion that he had "done nothing against our people or the customs of our fathers" makes it clear that Paul himself followed Jewish custom. 

Paul further underscored this distinction in Acts 21. When Paul came to Jerusalem, he met with the head elder of the Jerusalem church, James, along with the other elders. They expressed to him a concern about misinformation about Paul that had been spread throughout Jerusalem. The "many thousands … among the Jews" who had "believed" in Jesus "had been told about" Paul, that he was "teaching all the Jews who are among the Gentiles to forsake Moses, telling them not to circumcise their children nor to walk according to the customs." They suggest that Paul participate in a vow to demonstrate that he is doing no such thing, that he is also "zealous for the law," and Paul complies. 

There is no tension here, since religious custom is fine so long as it is not a substitute for faith. The argument Paul makes to the Gentiles is that by adopting a new custom as though it is a necessity, they negate the grace of God. In the letter to the Hebrews, the writer (likely Paul) makes it clear that although it is fine to follow religious customs, relying on them for righteousness is disobedience to God. The key to righteousness is obedience to Jesus from the heart. 

Paul insists that the key understanding of circumcision is to have our hearts set apart in obedience to God (Romans 2:29). As with this message in Genesis, New Testament believers are offered additional blessings if we are obedient and walk in faithfulness to God, in the newness of life. When we walk in obedience, we are walking with circumcised hearts.