Deuteronomy 7:3

neither … make marriages with them In the narratives in Genesis and Judges marriages are regarded as best when between members of the same family or tribe (Genesis 28:2; Genesis 28:8 f.) and as unfortunate when the wives are foreign (Genesis 26:34 f., Genesis 27:46; Judges 14:3). But no law against marriage with foreigners is either assumed or implied. On the contrary, Moses (Exodus 2:21), David (2 Samuel 3:3), Solomon (1 Kings 11:1), Ahab (1 Kings 16:31), all marry foreigners, and there are other instances (Bath-sheba and Uriah, etc.). The deuteronomic veto, therefore, may be assumed to be the earliest law against such marriages (Exodus 34:16 is editorial) and to have become necessary by the experience of their evil consequences, conducive to idolatry (Judges 3:5 f., deuteronomic). At the same time D allows marriage with a foreign woman taken in war (Deuteronomy 21:10). That the law was not kept is seen from the Book of Ezra.