Commentary for Genesis 42:7

ויתנכר אליהם HE MADE HIMSELF STRANGE UNTO THEM — He made himself like a נכרי a stranger to them in his conversation, speaking harshly (Genesis Rabbah 91:7).

AND JOSEPH SAW HIS BRETHREN, AND HE RECOGNIZED THEM. Immediately as he saw them he recognized them, and he feared lest they recognize him. And he made himself strange (‘vayithnakeir’) unto them by putting a mitre upon his forehead and part of the face, thus disguising himself, just as it is said concerning the wife of Jeroboam, Arise, I pray thee, and disguise thyself, that thou be not known to be the wife of Jeroboam,¹²³I Kings 14:1. Ramban explains the word vayithnakeir in a physical sense. Joseph disguised himself by placing his mitre over his face. Further on, Ramban mentions a second interpretation. See Note 126. and it further says, For it will be, when she cometh in, that she ‘mithnakeirah’ (will pretend to be another woman).¹²⁴Ibid., Verse 5. It may be that the word vayithnakeir here means that he made himself strange by his words, speaking to them harshly and asking them in anger — as if it were not customary to come before him to purchase food — “From where do you come to appear before me?” And they said, From the land of Canaan to buy food. When they mentioned this to him, it then became clear to him that they were indeed his brothers. This is the meaning of the expression, And Joseph recognized his brethren,¹²⁵Verse 8 here. which is mentioned a second time to indicate an additional sense of recognition and knowledge of the truth with respect to them.
Now Rashi wrote in explanation of the word vayithnakeir: “He made himself like a nochri (stranger) in conversation by speaking harshly to them.” According to Rashi’s opinion, the word vayithnakeir signifies that he spoke to them as a man who is a nochri (stranger). But this is not correct.¹²⁶A stranger does not necessarily speak harshly. Hence Rashi’s interpretation is incorrect. Ramban’s second interpretation mentioned above, however, is based upon the word vayithnakeir having the same root as heker (recognition), except that the word here changes its meaning so as to indicate its opposite. See Rashi on Exodus 27:3, where he says that there are many such words in the Hebrew language. In the case before us, the word vayithnakeir would thus mean that Joseph made himself unrecognizable by speaking harshly to them. See my Hebrew commentary, p. 232.

מאין באתם?; he pretended not to know who they were.