The idea of “circumcision of the heart” is found in Romans 2:29. It refers to having a pure heart, separated unto God. Paul writes, “No, a person is a Jew who is one inwardly; and circumcision is circumcision of the heart, by the Spirit, not by the written code. Such a person’s praise is not from other people, but from God.” It is easy to place more emphasis on religious effort (“confidence in the flesh”) than on internal faith, but God values the attitude of our hearts above all else. “For it is we who are the circumcision, we who serve God by His Spirit, who boast in Christ Jesus, and who put no confidence in the flesh.” (Phil 3:3) God notices all you do for Him and will reward you for it, but only if it comes as a loving response to His free gift of salvation.
Paul consistently taught that salvation begins and ends with God. We can do nothing to be saved on our merit–we must accept God’s gift of salvation. There is no other way to receive forgiveness from sin. We are chosen by God, and the Holy Spirit works within us to make us like Christ. “But we ought always to thank God for you, brothers and sisters loved by the Lord, because God chose you as firstfruits to be saved through the sanctifying work of the Spirit and through belief in the truth.” (2 Thess 2:13) God’s purpose for people wasn’t an afterthought; it was settled before the foundation of the world. If you have believed in Christ, you can rejoice in the fact that God has always known you. He will guide and protect you until one day you stand in His presence. “For those God foreknew He also predestined to be conformed to the image of His Son, that he might be the firstborn among many brothers and sisters” (Rom. 8:29)
We aren’t saved because we deserve it, but because God is gracious and freely gives salvation. We didn’t influence God’s decision to save us; He saved us according to His plan. “For He chose us in Him before the creation of the world to be holy and blameless in His sight. In love He predestined us for adoption to sonship through Jesus Christ, in accordance with His pleasure and will–to the praise of His glorious grace, which He has freely given us in the One He loves.” (Eph 1:4-6)
The Lord knows our weaknesses and knows we need help to be holy. “When the Advocate comes, whom I will send to you from the Father—the Spirit of Truth who goes out from the Father—He will testify about me.” (John 15:26) And it is in His power that we can live as Jesus wants us to. “For we know, brothers and sisters loved by God, that He has chosen you, because our gospel came to you not simply with words but also with power, with the Holy Spirit and deep conviction.” (1 Thess 1:4-5a)