"Whoever has been born of God does not sin, for His seed remains in him; and he cannot sin, because he has been born of God." 1 John 3:9)
N.T. Use of Seed
What is the seed which remains in the one who is born of God? At few possibilities exist. Natural seed (Gen. 1:11), biological seed (Rom. 1:3), spiritual seed (the word of God, Lk. 8:11; 1 Peter. 1:23), "good seed", (the children of God) and tares (the children of the wicked, Matt 13:38).
In the context of the New Testament, when the "seed" relates to people or children of God, it most often, if not always speaks of the "seed of Abraham". This is particularly true when there is a contrast between the children of God and the children of the devil. The context of 1 John is the children of God versus the children of the devil, 1 Jn. 3:10. For other examples, see Matt. 3:1-11; Matt. 13:1-43; John 8:33-44; Heb. 3, 1 Peter 1 and 2, Rev. 2:9, 3:9, and ch. 12.
Birth represents the idea of the raising up of seed. Consider this quote by the Sadducees who quote the Levirate marriage law from Deut. 25:5f. 'Teacher, Moses said that if a man dies, having no children, his brother shall marry his wife and raise up offspring for his brother. (Matt. 22:24). The word "offspring" in the text is translated from sperma (Greek), which means seed.
The Seed of Abraham
Those who are sown as children of God, are sown as the seed of Abraham. Christ is the seed of Abraham, as noted in the genealogy of Matthew (1:1-17). He is also the son of God being the son of Adam, (Lk. 3:23-38). Those who are born again of water and of the Spirit (Jn. 3:5) are like Christ, "sons of God" (Gal. 3:27) and sons (the seed) of Abraham, (Gal. 3:29).
Every natural child of Abraham, (blood descendants) including none blood descendants born in his house and those bought from foreigners who were uncircumcised, had to become circumcised. In so doing, they entered into the Abrahamic covenant. Any who were not circumcised were "cut off" from God's people because he had broken the covenant. (Gen. 17:12-14)
The Stranger To Receive An Inheritance
In the new eschatological temple of God, the stranger (one who is not a native born Israelite), but who entered the covenant, also received an inheritance.
Thus you shall divide this land among yourselves according to the tribes of Israel. It shall be that you will divide it by lot as an inheritance for yourselves, and for the strangers who dwell among you and who bear children among you. They shall be to you as native-born among the children of Israel; they shall have an inheritance with you among the tribes of Israel. And it shall be that in whatever tribe the stranger dwells, there you shall give him his inheritance says the Lord." (Ex. 47:21-22)
Contrary to Dispensationialism Premillenialism and other such views, this is not "third" physical temple. It is the new spiritual temple of God having Jesus Christ as it's chief corner stone, (Acts 4:11-12; 1 Cor. 3:16-17; Eph. 2;19-22; 1 Pet. 2:5-12). It is Christ and the Father, Rev. 21:3; 22, in the new Jerusalem. The name of this new city/temple is "THE LORD IS THERE" (Ezk. 48:35). That means wherever two or three are gathered in the name of Christ, he is there. In Christ, God's place of worship is no longer a geo-centric structure, (John 4:22-24).
Therefore, the prophet teaches that Christ is the new land and those who accept him, Jew and Gentiles, receive an inheritance in him. Gentiles become as "native born". That means they become sons of Abraham.
His Seed Remains in Him
While those who converted from Judaism were excommunicated by their brethren, (Jn. 9:22; 12:42-43), they did not lose their Abrahamic privilege and right to the inheritance. The seed of Abraham is transferred to believers through Jesus Christ. That is the meaning of "his seed remains in him".
As the Old Covenant stated, the believers' connection to Abraham is unbroken. In the case of a Gentile (stranger) he becomes as one native born who enters into and is entitled to the inheritance. "And if you are Christ's then are you Abraham's seed and heirs according to the promise, (Gal. 3:29).
Consequently, there is no such idea as "replacement theology" in declaring the church as the new Israel of God, i.e. Abraham's seed