Paul is convinced that the plan of salvation always included the Gentiles. He had plenty of Old Testament texts to support this conviction (Romans 15:8–12; 2 Samuel 22:50; Deuteronomy 32:43; Psalm 117:1; Isaiah 11:10).
If God always planned to include the Gentiles, why did He explicitly exclude them from the community throughout much of the Old Testament history? For example, if your mother or father was an Israelite but you were born of a forbidden marriage, which likely means your parent married someone who was not an Israelite, then you would be permanently excluded from the sanctuary worship (Deuteronomy 23:2). Ammonites and Moabites were also permanently banned from the sanctuary worship (Deuteronomy 23:3). Edomites and Egyptians were in a slightly better category. After three generations of faithful service to God, they could finally be included in the sanctuary worship of God (Deuteronomy 23:8).
The answer to this problematic question can found in the nature of the plan of salvation. The plan of salvation has only one Messiah. Since there is only one Messiah, He can only be born in one place, in one family, at one time. Since His death is sufficient to save all humanity, He only needs to die one time (Romans 6:10; Hebrews 9:26).
Immediately after the fall, God promised that the Messiah would come from the seed of Eve (Genesis 3:15). God then had to choose the specific family from which Messiah should be born. God chose the family of Abraham, because Abraham was a friend of God and would direct his children in the way of the Lord (Isaiah 41:8; Genesis 18:19). God further narrowed His choice for the lineage of the Messianic king to the tribe of Judah (Genesis 49:10) and then to the family of David (2 Samuel 7:12–16). Preserving the family of Abraham so that the Messiah could be born to the predetermined family, in the predetermined place (Micah 5:2), and minister and die at the predetermined time (Daniel 9:24–27) was essential to the plan of salvation.
Many of the restrictions God placed in the Old Testament were designed to preserve the family of Abraham so that the Messiah, the Savior of all peoples, could be born as the Old Testament predicted. Intermarriage with unbelievers would jeopardize the integrity of the Messianic line. The choice of Israel for the unique mission of being the family through whom the Messiah came necessitated their protection from potential spiritual and political enemies (Psalm 121:4–5, 7; Zechariah 2:8).
When the Messiah came, He was to be the Savior of the world (1 Timothy 4:10). With the coming of the Messiah, Israel’s first mission was complete, and an expanded mission of proclaiming the saving love of God for all humanity was given to the church. The earlier restrictions on Gentiles were no longer necessary. In fact, they were counterproductive to the inclusive saving message of Jesus.