The Literal Commandment
When the LORD your God brings you into the land where you are entering to possess it, and clears away many nations before you, the Hittites and the Girgashites and the Amorites and the Canaanites and the Perizzites and the Hivites and the Jebusites, seven nations greater and stronger than you, and when the LORD your God delivers them before you and you defeat them, then you shall utterly destroy them. You shall make no covenant with them and show no favor to them. Furthermore, you shall not intermarry with them; you shall not give your daughters to their sons, nor shall you take their daughters for your sons. (Deuteronomy 7:1-3)
The literal commandment is that we should not intermarry with the seven nations that were in the Land.