Rashi on Genesis 26:2/רש"י על בראשית כ״ו:ב׳

1אל תרד מצרימה GO NOT DOWN INTO EGYPT — Because he thought of going down to Egypt as his father had gone down in time of famine. He said to him, “Do not go down to Egypt for you are a burnt-offering without blemish and residence outside the Holy Land is not befitting you” (Genesis Rabbah 64:3).