Deuteronomy 23:6

And he smote Moab, and measured them with a line, casting them down to the ground; even with two lines measured he to put to death, and with one full line to keep alive. And so the Moabites became David's servants, and brought gifts.

And he brought forth the people that were therein, and put them under saws, and under harrows of iron, and under axes of iron, and made them pass through the brick-kiln: and thus did he unto all the cities of the children of Ammon. So David and all the people returned unto Jerusalem.

Now therefore give not your daughters unto their sons, neither take their daughters unto your sons, nor seek their peace or their wealth for ever: that ye may be strong, and eat the good of the land, and leave it for an inheritance to your children for ever.

In those days also saw I Jews that had married wives of Ashdod, of Ammon, and of Moab: And their children spake half in the speech of Ashdod, and could not speak in the Jews' language, but according to the language of each people. And I contended with them, and cursed them, and smote certain of them, and plucked off their hair, and made them swear by God, saying, Ye shall not give your daughters unto their sons, nor take their daughters unto your sons, or for yourselves.