Deuteronomy 23:6

¹²Now therefore don’t give your daughters to their sons. Don’t take their daughters to your sons, nor seek their peace or their prosperity forever, that you may be strong and eat the good of the land, and leave it for an inheritance to your children forever.’

²³In those days I also saw the Jews who had married women of Ashdod, of Ammon, and of Moab; ²⁴and their children spoke half in the speech of Ashdod, and could not speak in the Jews’ language, but according to the language of each people. ²⁵I contended with them, cursed them, struck certain of them, plucked off their hair, and made them swear by God, “You shall not give your daughters to their sons, nor take their daughters for your sons, or for yourselves.

²He defeated Moab, and measured them with the line, making them to lie down on the ground; and he measured two lines to put to death, and one full line to keep alive. The Moabites became servants to David, and brought tribute.

³¹He brought out the people who were in it, and put them to work under saws, under iron picks, under axes of iron, and made them go to the brick kiln; and he did so to all the cities of the children of Ammon. Then David and all the people returned to Jerusalem.