Midrash sobre Gênesis 18:32

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.

Hence they said: If there be fifty righteous in the world, the world exists through their righteousness. (Abraham) arose and began to beseech (God), and made supplication before Him until he brought (the number down to) ten. Hence (the sages said): (When there are) ten people in a place, the place is delivered by their righteousness, as it is said, "And he said, I will not destroy it for the sake of the ten" (Gen. 18:32).