Tafsir of Yusuf 12:58

They did not recognize him due to the long passage of time and his separation from them during his youth. Furthermore, they believed he had perished, and he had faded from their thoughts due to their lack of concern for him. The state of majesty and authority he had attained was so far removed from the state in which they had left him—cast into a well and sold for a few dirhams—that even if the thought had crossed their minds that it was him, they would have dismissed their own suspicions as false. Moreover, kingship alters one’s appearance and clothes the individual in such awe and grandeur that even those who knew him would fail to recognize him.

It is said: They saw him in the attire of Pharaoh, wearing silk garments, seated upon a throne, with a golden collar around his neck and a crown upon his head, so it never crossed their minds that it was him.

It is also said: They only saw him from a distance, with space and veils between them, and they stood only where those seeking favors would stand.

He, however, recognized them because he had parted from them when they were already men, and he saw their attire was similar to what it had been back then. Additionally, his focus was fixed upon them and the prospect of knowing them, so he observed and discerned.

Al-Hasan said: He did not recognize them until they made themselves known to him.