Rashi on Exodus 33:2/רש"י על שמות ל״ג:ב׳

1וגרשתי את הכנעני וגו׳ AND I WILL DRIVE OUT THE CANAANITE etc. — These are only six nations whilst in Deuteronomy 7:1 seven such are mentioned! But the Girgashites, the seventh, arose and emigrated of their own accord from before them (the Israelites) and therefore are not mentioned here amongst those who were driven out (Jerusalem Talmud Shevi'it 6:2; Leviticus Rabbah 17:6).