Deuteronomy 7:23
But the LORD thy God shall deliver them unto thee, and shall destroy them with a mighty destruction, until they be destroyed. But the LORD thy God shall deliver them unto thee, and shall destroy them with a mighty destruction, until they be destroyed.
The Lord Himself will deliver opposing enemies into the hand of His people and destroy them with mighty destruction until they are completely destroyed.
The promise belongs to Deuteronomy 4-8, which show what God required of His ancient people in order that they might be a holy people to Himself.
That instruction teaches God's people to obey His commandments and trust His faithful care.
It is to be read with the whole of Deuteronomy 7 and with Deuteronomy 1 and 8, especially Deuteronomy 7:6.
It was written for admonition for those on whom the ends of the world are come, and those words are to be studied and read with profit now.
This is because the day of God's great final review is near, when all the people of this world must stand before the Judge of all the earth to answer for their deeds.
The present is the time of investigation, when every character will be investigated and every case decided for eternity.