Midrash su Genesi 42:5

As soon as Jacob heard that there was corn in Egypt, he said to his sons: Get you down thither, and buy for us from them, etc. And Joseph’s ten brethren went down (ibid. 42:2–3). Why did all ten go? Because in that number resides the power to set aside retribution.⁴Because ten comprise a minyan and so they could beseech God as a congregation. For example, when the Holy One, blessed be He, was about to destroy Sodom, our patriarch Abraham pleaded for heavenly mercy in their behalf. He spoke first of fifty men, but finally reduced the number to ten, as it is said: Peradventure ten shall be found there (ibid. 18:31). Ten men also comprise a congregation, as is said: How long shall I bear with this evil congregation (Num. 14:27), and God standeth in the congregation of God (Ps. 82:1). Hence Scripture states: Joseph’s ten brethren went down (Gen. 42:3). Just as in the case of Sodom, Scripture speaks here of ten. And the sons of Israel came to buy among those that came (Gen. 42:5), in order that no one would recognize them. The Holy One, blessed be He, declared: Because you have said: We shall see what will become of his dreams (ibid. 37:20), his dream was fulfilled. Joseph saw his brothers and recognized them, but they did not recognize him, for they had felt no compassion for him, while Joseph recognized them because he pitied them.

And the men returned to Joseph and informed him thereof, and Joseph once more ‎dispatched sixteen of his servants to seek his brothers; and they went and dispersed ‎themselves towards the four corners of the city. And four of the servants went into the house ‎of the harlots and they found the ten men there seeking their brother. And those four men ‎took them, and they brought them before Joseph, and they bowed down before him to the ‎ground. And Joseph was seated upon his throne in his temple, robed in garments of white and ‎purple and upon his head was a large crown of gold and all the valiant men were around ‎him.And the sons of Jacob saw him, and his beautiful appearance and dignity surprised them, ‎and they once more bowed down before him to the ground, and when Joseph saw his ‎brothers he recognized them, but they recognized him not, because he was too great in their ‎eyes. And Joseph spoke unto them saying: Whence do you come? And all of them answered, ‎saying: Thy servants came from the land of Canaan to purchase food, for verily the famine is ‎heavy in all the earth, and when thy servants heard that there was food in Egypt we came ‎amongst the others to buy corn for our support. And Joseph answered unto them saying: And ‎if you have come to purchase food as ye have said, wherefore did you come through ten ‎different gates of the city? This cannot be otherwise but that you have come to spy out the ‎whole land. And they all together answered unto Joseph: Nay, my lord, we are honest men. ‎Thy servants have never been spies, but we have come to purchase food. For all of us, thy ‎servants, are the sons of one man, in the land of Canaan, and our father commanded unto us ‎saying: When you come unto the city do not enter into one gate, on account of the inhabitants ‎of the land. And Joseph answered unto them once more and he said: That is precisely what I ‎said unto you, that you have come to spy out the whole land, and, therefore, you have ‎entered ten different gates to see the nakedness of the land. And verily every one that comes ‎to purchase doth so, and he goeth his way; but ye are now three days in the land. And what ‎have ye done among the walls of the harlots, whence ye have been these three days? Verily ‎spies only will do such things. And they said unto Joseph: Far be it from our lord to speak these ‎words, for we are twelve brothers, the sons of our father, Jacob, in the land of Canaan, the ‎son of Isaac, the son of Abraham, the Hebrew. And behold the youngest is this day with our ‎father, and one is not here. For he hath been lost from us, and we said: Peradventure he is in ‎this land. And we searched for him in all the land of Egypt, and we came unto the house of the ‎harlots also to seek him there. And Joseph said unto them: And have you searched for him in ‎all the earth, that there is not left another place but Egypt to seek him in?‎