Vayigash 

ויגש

Joseph presented his brothers to Pharaoh, who asked them about their occupations and habits. Joseph did not choose the strongest among them, so that Pharaoh would not want to recruit them into his army. 

“And from among [literally, the edge of] his brothers he took five men, and he presented them before Pharaoh” (Genesis 45:27). Why does the verse say: “From the edge of his brothers”? The verse comes to teach you that the brothers Joseph took to Pharaoh were not the mightiest among the tribes. And who were the five men he took? Reuben, Simeon, Levi, Benjamin, and Issachar. Why did Joseph the righteous take these five from among his brothers? Because he knew the strength of each one of his brothers, and he spoke wisely, and said: If I present the mighty among them to Pharaoh, he will see them and make them his soldiers. Therefore, Joseph presented these five men, who were not [as] mighty.  <source>(<i>Bereshit</i> <i>Rabba</i> [Theodor-Albeck] 95) </source>