Throughout the Old Testament, we see the character of the patriarchs or "founders" of a tribe/family of people reflected in further generations, and in blessings or curses upon them. Abraham himself had cursed the Canaanites, but knew that God had promised an inheritance through his son Isaac, so he made his servant swear to see that Isaac would marry among his own people, so that his descendants would be a pure line of "chosen people".

Genesis 24:3-4