Esdras 10

Esdras 10:9

I will say what the Apostle has taught me, that they are not on the side of righteousness, but of iniquity: not of light, but of darkness: that they do not belong to Christ, but to Belial: that they are not temples of the living God, but shrines and idols of the dead. And, if you wish to see more clearly how utterly unlawful it is for a Christian woman to marry a Gentile, consider what the same Apostle says, [1 Corinthians 7:39] "A wife is bound for so long time as her husband lives: but if the husband be dead, she is free to be married to whom she will; only in the Lord," that is, to a Christian. He who allows second and third marriages in the Lord, forbids first marriages with a Gentile. Whence Abraham also makes his servant swear upon his thigh, that is, on Christ, Who was to spring from his seed, that he would not bring an alien-born as a wife for his son Isaac. And Ezra checked an offense of this kind against God by making his countrymen put away their wives. — Against Jovinianus (Book I), Section 10