Midrash su Genesi 42:13

"And Yosef saw his brothers, etc." - Rabbi Yehoshua bar Nechemiah said, "He made himself a stranger (nocri) to them. "And Yosef recognized his brothers, etc." - Rabbi Levi and the Rabbis [argued about this]: Rabbi Levi said, "At the time they fell into his hand, 'And Yosef recognized his brothers;' at the time he fell into their hands, 'and they did not recognize him.'" And the Rabbis said, "He who left them adorned by beards, 'And Yosef recognized his brothers - and they did not recognize him,' as they did not leave him adorned by a beard [as he was too young].""And Yosef remembered, etc... and he said to them, etc...'we are all the sons of one man'" - they had a flash of Divine inspiration [in which] they said to him, "We and you are the sons of one man, we are." He said to them, "And where is [the other one]?" "We sold him." He said to them, "For how much did you sell him?" They said to him, "For five sela."He said to them, "And if a person would say to you, 'Give me five sela and I will give him to you,' would you do it?" They said to him, "Yes." "And if a person would say to you, 'Give me double and I will give him to you,' would you do it?" They said, "Yes." "And if a person would say to you, '[Even] if you would give me a thousand, I will not give him to you,' what would you do?" They said to him, "For that have we come down [to Egypt], whether to kill or to be killed." He said to them, "'This is what I have said about you, spies, etc.'" "Through this will you be examined; by the life of Pharaoh" - when he wanted to make a false oath, he would swear by the life of Pharaoh. Rabbi Levi said, "There is a parable of a goat that ran away from the pasture and went in to a widow. What did she do? She got up and slaughtered it and flayed it and put it in her bed and covered it with a sheet. They came to request it from her. She said, 'So should happen to this woman if she knows about it, this flesh [actually referring to the goat] should be bitten and eaten.' So too, 'by the life of Pharaoh if you will get out, etc...Send one of you.'" "And he placed them in the prison for three days" - never does the Holy One, blessed be He, leave righteous ones in dire straits for three days and so was it taught to Yosef, to Yonah, to Mordechai, to David. And so is it stated (Hoshea 6:2), "He will revive us from the two days; on the third day" of the tribes, "He will bring us up" - "And Yosef said to them on the third day."