פירוש על בראשית 42:8

'ויכר יוסף וגו AND JOSEPH RECOGNISED HIS BRETHREN etc. — because, when he left them they were full-bearded (Yevamot 88a).

BUT THEY DID NOT RECOGNIZE HIM. I.e., at all. And so he no longer needed to make himself appear strange to them. Now in this matter of recognition, our Rabbis have said¹²⁷Kethuboth 27b. that Joseph recognized his brothers because he had left them bearded, but they did not recognize him because when he left them he had no beard and now they found him with a beard.
Now Issachar and Zebulun were but a little older than Joseph,¹²⁸Thus they were also beardless when Joseph left, so how did he recognize them now that they were bearded? but having recognized the older ones, he recognized them all. Moreover, he recognized them because he knew they were bound to come, but they did not recognize him because it did not occur to them that a slave sold to the Ishmaelites should be the ruler of a land.
Rabbi Abraham ibn Ezra says: And he recognized them.¹²⁹Verse 7 here. That is, at first he recognized them to be his brothers, and following that, he looked at each one and recognized him individually.¹³⁰This explains the repetition in Verse 8, And Joseph recognized his brethren, since it refers to individual recognition.

והם לא הכירוהו. Joseph had grown a beard, something, which at 17, when they had last seen him, he had not yet had. Furthermore, the Royal garments were something they would not have associated with their brother. They did not recognise his voice either, as they had never heard him speak Egyptian. Joseph made sure that there was always an interpreter between him and his brothers as we know from verse 23.

ויכר יוסף את אחיו, now he recognised them each individually

ויכר יוסף את אחיו. Joseph recognised his brothers. Joseph had no trouble recognising his brothers since they all wore beards when he left them. Although it is normal for acquaintances who have not seen each other for a long time to recognise one another, i.e. that as soon as one person recognises the second person, he in turn suddenly is able to recognise the first person also, this was not the case here. Normally the heart communicates secrets as we know from Proverbs 27,19 "man's heart will be reflected by his counterpart;" the Torah reveals that in this instance this phenomenon did not work. The reason was that Joseph's exalted position stifled any glimmer of recognition there might have been on the part of the brothers.

ויכר יוסף, as we already explained on verse 7. The reason the Torah has repeated this is that the Torah wished to emphasise that he showed them brotherly love by not harming them or killing them, whereas they, at the time had not shown him any brotherly feelings in their treatment of him, first planning to kill him, then stripping him, throwing him into the pit, and subsequently selling him into slavery.

והם לא הכירוהו, “but they did not recognize him.” Joseph had left his father’s house before he had grown a beard, and in the meantime his beard had materially changed his facial features. Although we must assume that Issachar and Zevulun who were hardly older than he had also not had a beard at the time when he left his father’s house, the fact that he had identified eight of the ten brothers who had had beards before he left home, made it easy for him to also recognize the other two. Furthermore, he enjoyed the advantage of having known with certainty that his brothers would come to Egypt to buy grain. He therefore kept a special watch for their arrival. The fact that Pharaoh had changed his name also made it more difficult for his brothers to suspect that someone by that name was their brother. In addition, Joseph now spoke Egyptian whereas they spoke Hebrew.

ויכר יוסף את אחיו, “Joseph recognised his brothers;” because they addressed each other with their names, and he understood both their names and the language in which they spoke.

והם לא הכירהו BUT THEY RECOGNISED HIM NOT — because when he left them he had no beard whereas now he had grown a beard.

והם לא הכירוהו, “but they did not recognise him;” one reason was that he had grown a beard that he did not have when he was sold. Secondly, his name had been changed. Thirdly, he now spoke Egyptian and he used an interpreter, making believe that he did not understand Hebrew.

A Midrashic explanation is: ויכר יוסף את אחיו JOSEPH RECOGNISED HIS BRETHREN — Now that they were in his power he recognised them as his brothers and had pity on them, והם לא הכירהו but when he fell into their power, “they did not recognize him” as their brother, by acting towards him in brotherly manner (Genesis Rabbah 91:7).