Genesis 3:15), and then this "seed" was further defined and restricted (Abraham, Isaac, Jacob, Judah, . . . David, . . . Christ -- see Galatians 3:15-16).
So far as I can tell, it was not so much a matter of these women being foreign (non Jewish by race), but a matter of these women worshipping foreign gods, that was at issue. The concern was always that men's hearts would be turned from God to idols, as it were (Deuteronomy 7:1-5; Joshua 23:12-13; Judges 3:1-6; 1 Kings 11:1-8).
If marriage is a picture of the relationship of Jesus Christ to His bride, the church (all true believers), then marriage to a believer of another race simply pictures the fact that Jesus came to save Gentiles as well as Jews -- a truth unbelieving Jews were not willing to accept (see here Matthew 3:9; Luke 4:16-30; Acts 22:21-22).
This topic of interracial marriage is a great place to proclaim the Gospel.
I hope this will help you get started.
5 Now may the God of endurance and comfort give you unity with one another in accordance with Christ Jesus, 6 so that together you may with one voice glorify the God and Father of our Lord Jesus Christ. 7 Receive one another, then, just as Christ also received you, to God's glory. 8 For I tell you that Christ has become a servant of the circumcised on behalf of God's truth to confirm the promises made to the fathers, 9 and thus the Gentiles glorify God for his mercy. As it is written, "Because of this I will confess you among the Gentiles, and I will sing praises to your name." 10 And again it says: "Rejoice, O Gentiles, with his people." 11 And again, "Praise the Lord all you Gentiles, and let all the peoples praise him." 12 And again Isaiah says, "The root of Jesse will come, and the one who rises to rule over the Gentiles, in him will the Gentiles hope" (Romans 15:5-12)
Also, I just found this article by John Piper, who is always a most worthy source: