Exodus 23:32-33

23:32 “You must make no covenant with them or with their gods. 23:33 They must not live in your land, lest they make you sin against me, for if you serve their gods, it will surely be a snare to you.”

Exodus 34:16

34:16 and you then take his daughters for your sons, and when his daughters prostitute themselves to their gods, they will make your sons prostitute themselves to their gods as well.

Deuteronomy 7:3-4

7:3 You must not intermarry with them. Do not give your daughters to their sons or take their daughters for your sons, 7:4 for they will turn your sons away from me to worship other gods. Then the anger of the Lord will erupt against you and he will quickly destroy you.

Joshua 23:12-13

23:12 But if you ever turn away and make alliances with these nations that remain near you, and intermarry with them and establish friendly relations with them, 23:13 know for certain that the Lord our God will no longer drive out these nations from before you. They will trap and ensnare you; they will be a whip that tears your sides and thorns that blind your eyes until you disappear from this good land the Lord your God gave you.

Ezra 9:12

9:12 Therefore do not give your daughters in marriage to their sons, and do not take their daughters in marriage for your sons. Do not ever seek their peace or welfare, so that you may be strong and may eat the good of the land and may leave it as an inheritance for your children forever.’

Ezra 10:2-17

10:2 Then Shecaniah son of Jehiel, from the descendants of Elam, addressed Ezra:

“We have been unfaithful to our God by marrying foreign women from the local peoples. Nonetheless, there is still hope for Israel in this regard. 10:3 Therefore let us enact a covenant with our God to send away all these women and their offspring, in keeping with your counsel, my lord, and that of those who respect the commandments of our God. And let it be done according to the law. 10:4 Get up, for this matter concerns you. We are with you, so be strong and act decisively!”

10:5 So Ezra got up and made the leading priests and Levites and all Israel take an oath to carry out this plan. And they all took a solemn oath. 10:6 Then Ezra got up from in front of the temple of God and went to the room of Jehohanan son of Eliashib. While he stayed there, he did not eat food or drink water, for he was in mourning over the infidelity of the exiles.

10:7 A proclamation was circulated throughout Judah and Jerusalem that all the exiles were to be assembled in Jerusalem. 10:8 Everyone who did not come within three days would thereby forfeit all his property, in keeping with the counsel of the officials and the elders. Furthermore, he himself would be excluded from the assembly of the exiles.

10:9 All the men of Judah and Benjamin were gathered in Jerusalem within the three days. (It was in the ninth month, on the twentieth day of that month.) All the people sat in the square at the temple of God, trembling because of this matter and because of the rains.

10:10 Then Ezra the priest stood up and said to them, “You have behaved in an unfaithful manner by taking foreign wives! This has contributed to the guilt of Israel. 10:11 Now give praise to the Lord God of your fathers, and do his will. Separate yourselves from the local residents and from these foreign wives.”

10:12 All the assembly replied in a loud voice: “We will do just as you have said! 10:13 However, the people are numerous and it is the rainy season. We are unable to stand here outside. Furthermore, this business cannot be resolved in a day or two, for we have sinned greatly in this matter. 10:14 Let our leaders take steps on behalf of all the assembly. Let all those in our towns who have married foreign women come at an appointed time, and with them the elders of each town and its judges, until the hot anger of our God is turned away from us in this matter.”

10:15 Only Jonathan son of Asahel and Jahzeiah son of Tikvah were against this, assisted by Meshullam and Shabbethai the Levite. 10:16 So the exiles proceeded accordingly. Ezra the priest separated out by name men who were leaders in their family groups. They sat down to consider this matter on the first day of the tenth month, 10:17 and on the first day of the first month they finished considering all the men who had married foreign wives.

Malachi 2:11

2:11 Judah has become disloyal, and unspeakable sins have been committed in Israel and Jerusalem. For Judah has profaned the holy things that the Lord loves and has turned to a foreign god!