Commentaire sur La Genèse 42:5

בתוך הבאים AMONG THOSE THAT CAME — They hid themselves in the crowd that people should not recognize them, for their father had bidden them not to show themselves all at one entrance to the city but that each should enter by a different gate in order that the evil eye should not have power over them (i.e. that they should not attract the envious attention of the people) for they were all handsome and stalwart men (Midrash Tanchuma 1.:10:6).

בתוך הבאים, people traveled together in large groups to afford themselves protection against highway robbers. At that time there were more than the usual amount of these. They would rob both the money carried to buy food and the food itself

ויבאו בני ישראל…כי היה רעב, The children of Israel arrived…for there was a famine in the land of Canaan. The fact that there was a famine had to be repeated. This is to explain why the Torah first wrote בתוך הבאים. You should not ask where these הבאים have been mentioned previously so that the Torah could describe the brothers as "being amongst them." Once we are told that there was a famine in Canaan it becomes obvious that many other people from Canaan must have been going to Egypt to buy grain there.