Definition and Context
Mixed marriages, in the biblical context, refer to unions between individuals of different faiths or religious backgrounds. This concept is primarily discussed in the context of Israelites marrying non-Israelites, which often involved marrying those who worshiped other gods. The concern was not ethnic but religious, as these marriages could lead to idolatry and a departure from the worship of Yahweh.

Old Testament References
The Old Testament contains several admonitions against mixed marriages. In Deuteronomy 7:3-4, the Israelites are explicitly commanded, "Do not intermarry with them. Do not give your daughters to their sons or take their daughters for your sons, for they will turn your children away from following Me to serve other gods." This directive was intended to preserve the religious purity and devotion of the Israelite community.

The narrative of Solomon in 1 Kings 11:1-4 illustrates the dangers of mixed marriages. Solomon's many foreign wives led him astray, as "his wives turned his heart after other gods, and his heart was not fully devoted to the LORD his God." This passage highlights the spiritual peril associated with marrying those who do not share the same faith.

Ezra and Nehemiah also address the issue of mixed marriages during the post-exilic period. In Ezra 9:1-2, the leaders report that "the people of Israel, including the priests and Levites, have not kept themselves separate from the neighboring peoples with their detestable practices." Ezra's response was one of mourning and prayer, leading to a covenant renewal and the separation from foreign wives (Ezra 10).

New Testament Perspective
The New Testament does not explicitly prohibit mixed marriages but emphasizes the importance of shared faith within marriage. In 1 Corinthians 7:12-14, Paul addresses believers married to unbelievers, advising them not to divorce if the unbelieving spouse is willing to live with them. This passage suggests a more nuanced approach, recognizing the sanctifying influence a believing spouse can have on the family.

However, 2 Corinthians 6:14-15 warns against being "unequally yoked with unbelievers," which is often interpreted as a caution against mixed marriages. The passage asks, "For what partnership can righteousness have with wickedness? Or what fellowship does light have with darkness?" This metaphor of unequal yoking underscores the potential spiritual discord in such unions.

Theological Implications
The primary concern with mixed marriages in the biblical narrative is the potential for spiritual compromise and the dilution of faith. The biblical texts emphasize the importance of maintaining religious integrity and devotion to God. The warnings against mixed marriages are rooted in the desire to protect the community from idolatry and to ensure the transmission of faith to future generations.

Practical Considerations
In contemporary application, the principles derived from these biblical texts encourage believers to consider the spiritual implications of marriage. While cultural and social factors are significant, the shared commitment to faith is paramount. The biblical narrative suggests that a marriage grounded in mutual faith can foster spiritual growth and stability, while a mixed marriage may present challenges to maintaining a unified spiritual life.

Conclusion
The biblical perspective on mixed marriages is complex, balancing the call to faithfulness with the realities of human relationships. While the Old Testament provides clear prohibitions, the New Testament offers guidance for those already in mixed marriages, emphasizing the transformative power of faith and the importance of spiritual unity.