We are all sinners, thus separated from God. And he has adopted us by having Jesus die on the cross for our sins. And when we accept that gift of forgiveness he adopts us into his family. And that is through his grace…
Ephesians 1: 5-7
5 he[b] predestined us for adoption to sonship[c] through Jesus Christ, in accordance with his pleasure and will— 6 to the praise of his glorious grace, which he has freely given us in the One he loves. 7 In him we have redemption through his blood, the forgiveness of sins, in accordance with the riches of God’s grace
When Jesus came, he told the Jews that you can’t get to heaven by works, or please God by your works. You’re always in the hole! He said what matters is your ethics not about which rules you follow but your faith in Christ. Your exterior doesn’t matter but your heart does. These verses explain it well:
Ephesians 2: 11-13
11 Therefore, remember that formerly you who are Gentiles by birth and called “uncircumcised” by those who call themselves “the circumcision” (which is done in the body by human hands)— 12 remember that at that time you were separate from Christ, excluded from citizenship in Israel and foreigners to the covenants of the promise, without hope and without God in the world. 13 But now in Christ Jesus you who once were far away have been brought near by the blood of Christ.
In Pauls’ epistles, he covers a lot adoption and inheritance. The Gentiles were separated from the Jews in many ways- one commonly being Circumcision. But God said let your hearts be circumcised not your flesh. And by adoption Jews and Gentiles are one in Christ. And then you inherit the promises of God.
Western Lit, essay 101.