Deuteronomy 23:6

You shall not promote their welfare or their prosperity all your days {forever}.

Ezra 9:12

Therefore, do not give your daughters to their sons, and do not take their daughters for your sons. Do not seek their peace and prosperity so that forever you may be strong and eat the good of the land and may give it as an inheritance to your sons.'

2 Samuel 8:2

When he defeated Moab, he measured them with the cord, making them lie on the ground. He measured two cords to kill and {the third cord} to let live. So Moab became servants of David, bringing tribute.

2 Samuel 12:31

He also brought out the people who [were] in it and put them to the saws and to the iron picks and to the iron axes, and he sent them to the place of the brickmakers. Thus he used to do to all the cities of the {Ammonites}, and he and all of the army returned to Jerusalem.

Nehemiah 13:23-25

Also in those days I saw Jews who had married women of Ashdod, Ammon, and Moab.

Treasury of Scripture Knowledge

Summary

Thou shalt not seek their peace nor their prosperity all thy days for ever.

Bible References

Thou shalt

2 Samuel 8:2
When he defeated Moab, he measured them with the cord, making them lie on the ground. He measured two cords to kill and {the third cord} to let live. So Moab became servants of David, bringing tribute.
2 Samuel 12:31
He also brought out the people who [were] in it and put them to the saws and to the iron picks and to the iron axes, and he sent them to the place of the brickmakers. Thus he used to do to all the cities of the {Ammonites}, and he and all of the army returned to Jerusalem.
Ezra 9:12
Therefore, do not give your daughters to their sons, and do not take their daughters for your sons. Do not seek their peace and prosperity so that forever you may be strong and eat the good of the land and may give it as an inheritance to your sons.'
Nehemiah 13:23
Also in those days I saw Jews who had married women of Ashdod, Ammon, and Moab.