2 Cor 11:4, Gal 1:6-9
Ezra wept when he heard that the people of Israel and the priests were still marrying Gentile daughters. (Ezra 9:1-3)
Ezra 9:1 Now when these things were done, the princes came to me, saying, The people of Israel, and the priests, and the Levites, have not separated themselves from the people of the lands, doing according to their abominations, even of the Canaanites, the Hittites, the Perizzites, the Jebusites, the Ammonites, the Moabites, the Egyptians, and the Amorites. 2 For they have taken of their daughters for themselves, and for their sons: so that the holy seed have mingled themselves with the people of those lands: yea, the hand of the princes and rulers hath been chief in this trespass. 3 And when I heard this thing, I rent my garment and my mantle, and plucked off the hair of my head and of my beard, and sat down astonied.
In the Old Testament, the people of Israel drove out all foreign women and children and decided to follow God's law. (Ezra 10:3)
Ezra 10:3 Now therefore let us make a covenant with our God to put away all the wives, and such as are born of them, according to the counsel of my lord, and of those that tremble at the commandment of our God; and let it be done according to the law.
If you preach any other gospel than the gospel that Jesus is the Christ, you will be cursed. (2 Corinthians 11:4, Gal 1:6-8)
2 Corinthians 11:4 For if he that cometh preacheth another Jesus, whom we have not preached, or if ye receive another spirit, which ye have not received, or another gospel, which ye have not accepted, ye might well bear with him.
Gal 1:6 I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel: 7 Which is not another; but there be some that trouble you, and would pervert the gospel of Christ. 8 But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.