42 18 Joseph said to them on the third day, “Do this and live, for I’m a God-fearing man. 19 If you are honest, let one of your brothers remain in this prison, and the rest of you go and take provisions to supply your famine-hungry households.20 Then, bring your youngest brother back to me to prove your words are truthful, and you will not die.”
They prepared. 21 Each brother said to the other, “It is true that we are guilty for our brother when we saw his heart’s distress. When he pleaded with us for mercy, we did not listen. That is why this distress has now come to us.”
22 Reuben declared to them, “Didn’t I say, ‘Do not wrong the boy’? But you would not listen. Now his blood demands requital.”
23 They did not know that Joseph understood them because there was an interpreter between them. 24 He stepped away from them and wept.
When he was able to return, he spoke to them and, he took Simeon from them and put him in fetters before their eyes.
After three days of imprisonment, Joseph changes the charge he made that one brother will be sent to bring Benjamin to Egypt (not father Jacob/Israel). Now the offer is to keep one brother imprisoned here while the other nine return to fetch Benjamin. In both cases, the question is which brother should go or which to stay. In each case, the brother chosen may be different.
Reuben spoke up to declare the guilt of the brothers for selling Joseph into Ishmaelite hands. It was he who had secretly planned to release Joseph for his own purposes. There is no indication that Reuben would have been chosen by the brothers to go home for Benjamin. He had already shown a willingness to betray them for his own benefit when Joseph was in the dry pit.
At this point, readers learn that Joseph had tricked the brothers by only speaking to them through an interpreter. The brothers did not understand that Joseph understood them—he no longer had a Hebrew accent when speaking Egyptian.
After a break to control his emotions after hearing Reuben’s confession on behalf of all the brothers, Joseph returns and is the one to choose Simeon to be the one held captive.
Why Simeon was selected is difficult to determine. Simeon, second born of Leah, may simply be the oldest after Reuben, who Joseph exempts after his confession.
All we have otherwise heard about Simeon is his being named and then his joining with Levi to slaughter the newly circumcised Shechemites. Neither of these issues would particularly concern Joseph and his path to the center.