So telling his people to stick with their own isn't enough?
He shouldn't be able to trust his people to remain separate?
No, apparently not.
All throughout the old testament the Hebrews were chastised when they strayed outside their own people.
In one portion of the scripture they were even told to send their bastard(mixed blooded) children and wives away.
But king Solomon loved many strange women, together with the daughter of Pharaoh, women of the Moabites, Ammonites, Edomites, Zidonians, [and] Hittites; 1 Kings 11:1
15 And Moses said unto them, Have ye saved all the women alive?
16 Behold, these caused the children of Israel, through the counsel of Balaam, to commit trespass against the LORD in the matter of Peor, and there was a plague among the congregation of the LORD.
17 Now therefore kill every male among the little ones, and kill every woman that hath known man by lying with him.
18 But all the women children, that have not known a man by lying with him, keep alive for yourselves. Numbers 31
3 And Elimelech Naomi's husband died; and she was left, and her two sons.
4 And they took them wives of the women of Moab; the name of the one [was] Orpah, and the name of the other Ruth: and they dwelled there about ten years. Ruth 1
And the children of Israel took [all] the women of Midian captives, and their little ones, and took the spoil of all their cattle, and all their flocks, and all their goods. Numbers 31:9
10 And the congregation sent thither twelve thousand men of the valiantest, and commanded them, saying, Go and smite the inhabitants of Jabeshgilead with the edge of the sword, with the women and the children.
11 And this [is] the thing that ye shall do, Ye shall utterly destroy every male, and every woman that hath lain by man.
12 And they found among the inhabitants of Jabeshgilead four hundred young virgins, that had known no man by lying with any male: and they brought them unto the camp to Shiloh, which [is] in the land of Canaan.
13 And the whole congregation sent [some] to speak to the children of Benjamin that [were] in the rock Rimmon, and to call peaceably unto them.
14 And Benjamin came again at that time; and they gave them wives which they had saved alive of the women of Jabeshgilead: and yet so they sufficed them not. Judges 21