אמר להם יוסף: 'לא כך אמרתם - שאחיו של זה מת? אני אקראנו ויבא אצלכם!', והיה קורא: 'יוסף בן יעקב, בוא אצלי! יוסף בן יעקב, בוא אצלי!'. והיו מסתכלין בארבע פינות הבית - אמר להם: 'מה אתם רואים?! אני יוסף אחיכם!'. מיד פרחה נשמתן, שנאמר " וְלֹא יָכְלוּ אֶחָיו לַעֲנוֹת אֹתוֹ כִּי נִבְהֲלוּ מִפָּנָיו" (בראשית מ"ה, ג), ולא האמינו לו עד שפרע עצמו והראה להם המילה. בראשית רבה צ"ג, ח.I am depressed, slept all day and am unable to work. No reason at all. To find escape and consolation I read the Weekly Portion of the Bible. Joseph is vice-king in Egypt, and his brothers come down from Hebron because there is hunger in the land and heard that there is corn in Egypt. Joseph says: "You say your brother Joseph is dead? I shall call him and he will come! Joseph son of Yakov, come here!". And he looked into the four corners of the room. "What do you see?" Joseph's brothers are seized by terror. "I am your brother Joseph!". They dont believe him. Then Joseph asks them to come near and he shows them his penis.
The Rav Finkelstein explains this strange passage. Joseph shows his circumcised penis to the wandering sons of Yakov to prove that he is indeed a Jew. But we know that Egyptians were circumcised, the mummies are circumcised, and Joseph brothers surely were aware of it. So what is all about? Archeology explains it all. Joseph was in Egypt during the rule of the Hyksos, a foreign uncircumcised people, and his brothers supposed that he was one of them. It was obvious that Joseph was not Egyptian, so his circumcision was the definitive proof of his Jewishness, of being a son of our father Yakov.
The Hyksos were a small foreign minority in Egypt that conquered the South almost without a battle in a period of internal strife. This fact explains the easy insertion of Joseph in their rule, and why Yakov's clan was invited to settle in Egypt. The Hyksos were few and in need of loyal allies. The Bible tells us that in the next generation, a new ruler "that did not knew of Joseph" took power in Egypt, and the anti-Egyptian tribe of Yakov was enslaved and their population growth watched with increasing worry. But that is another chapter.