Midrasch zu Bereschit 41:56

And Joseph opened his storehouses and placed officers over them, and they sold food to all ‎comers day after day. And Joseph knew that his brothers also would come into Egypt to buy ‎food, for the famine prevailed in all the earth. And Joseph commanded his people to ‎pronounce it through all Egypt saying: It is the pleasure of the king and his second and their ‎great men that everyone wishing to buy corn in Egypt should not send his servants but his ‎sons. And any man in Egypt or Canaan that cometh from all these lands to purchase corn in ‎Egypt, and he will go and sell it in any land the same shall be put to death. For no man will be ‎allowed to buy more than to supply his household. And further, every man that cometh ‎leading two or three beasts shall die, for no man shall bring more than his own beast. And ‎Joseph placed guards in the gates of Egypt, and he commanded them, saying: Every man that ‎cometh to buy food shall not be permitted until he hath written down his name, and the ‎name of his father, and the name of his father's father, and all the names registered through ‎the day shall be forwarded unto me in the evening, that I may know their names. And Joseph ‎did all these things and he made all these laws in order to know when his brothers. should ‎come to Egypt to buy food. And day after day Joseph’s men announced these laws through ‎the land so that all the people in the country east and west and all the earth knew the laws ‎which Joseph made in Egypt. And all the people, from all the ends of the earth came to buy ‎food in Egypt, and then they went on their way. And the princes of Egypt did as Joseph had ‎commanded, and all that came into Egypt to buy food were caused by the guards to write ‎down their names and the names of their father, and the register was brought unto Joseph in ‎the evening of each day. ‎And Jacob heard after this that there was food for sale in Egypt, and he called upon his sons to go into ‎Egypt to purchase corn, for the famine was heavy upon them likewise. And he said unto them: Behold, ‎I have heard there is corn for sale in Egypt, and all the world goes thither to purchase, and now why ‎should ye seventy be better than all the people of the earth? Go ye likewise down into Egypt and ‎purchase a little food among the many that go thither.