Is the Bible for or against it?
Endogamy is “the practice of marrying within a specific ethnic group, class, or social group, rejecting others on such bases as being unsuitable for marriage or other close personal relationships” — an unfamiliar term to many, but a very familiar practice, whether the criteria is racial, cultural, or religious.
In general, the Bible teaches that the people of God should only marry other people of God. In the Old Testament, this manifested in verses such as:
“You shall make no covenant with them [the Canaanites] and show no mercy to them. You shall not intermarry with them, giving your daughters to their sons or taking their daughters for your sons, for they would turn away your sons from following me, to serve other gods.” (Deut 7:1-4)
And in the New Testament:
A wife is bound to her husband as long as he lives. But if her husband dies, she is free to be married to whom she wishes, only in the Lord.” (1 Cor 7:39)
In these cases, the focus of the rule is not racial or cultural, but religious — it’s about people who serve the Lord. The rule exists partly for pragmatic reasons — a marriage where one partner does not share faith in the Lord has corrosive effects on the other partner (see “Does 2 Corinthians 6:14-15 mean that believers should not marry unbelievers?“). It is also a matter of symbolism — there’s a whole set of allegories between our personal marriages and the relationship of Christ and the Church, culminating in Rev 19:7-9.
To summarize, the Bible is for endogamy on limited grounds.