Intermarriage or Idolatry?

Intermarriage does not appear to have been forbidden in and of itself, but rather because it was a means to idolatry (e.g. Deut. 7:3ff.; Ezra 9:1-2). That is, the problem being addressed was idolatry, not the marriage of people from different ancestries. When intermarriage resulted in conversion to Israel's religion, it was acceptable (e.g. Num. 12:1ff.; Ruth 1:16; 4:10ff.; 1 Kings 11:4-8; Matt. 1:5). In Deuteronomy 21:10-14, the assumption is that by in becoming part of the husband's household, the captured wife will adopt the husband's religion. When this does not happen, the husband defiles the purity of Israel. When the wife does convert, the purity of Israel is not defiled -- the purity of Israel is a purity of faith and righteousness, not of blood (cf. Rom. 2:17-29; 4:1ff.).