Wajaa ikhwatu yoosufa fadakhaloo AAalayhi faAAarafahum wahum lahu munkiroon (surah Yusuf: 58)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(12:58) Joseph's brothers came to Egypt and presented themselves before him. *50 He recognized them but they did not. *51

Wa jaaa`a ikhwatu Yoosufa fadakhaloo `alaihi fa`arafahum wa hum lahoo munkiroon

*50) The events of several years after his coming into power have been left out for the sake of brevity, and the story has been resumed from the time when the brothers of Prophet Joseph came to Egypt, and paved the way for the eventual settlement of the Israelites in Egypt. It will, however, be worthwhile to have a glimpse of those events. During the first seven years of his reign, there was abundance of corn as he had predicted while interpreting the dream of the king. Accordingly he adopted all the measures he had put before the king concerning the years of plenty. Then the seven years of scarcity began and famine reigned not only over Egypt but all over the adjoining countries. Accordingly, Syria, Palestine, Trans-Jordan and the Northern part of Arabia began to suffer from the scarcity of food, but there was plenty of it in Egypt in spite of famine because of the wise steps Prophet Joseph had taken as a safeguard. That was why his brothers, like other neighbouring people, were forced by circumstances to go to Egypt and present themselves before him. It appears that Prophet Joseph had so arranged things that no foreigner was allowed to buy corn without a special permit from him. Therefore when the brothers reached Egypt, they might have had to present themselves before him for obtaining the special permit for buying the fixed quantity allowed under the famine regulations.
*51) It is no wonder that his brothers could not recognize Prophet Joseph, for, when they cast him into the well, he was merely a lad of seventeen and at the time of their meeting, he was a grown up man of thirty-eight years or so. Naturally, he must have changed in form during this long period. Besides, they could never have imagined that the brother whom they had cast into the well had become the ruler of Egypt.