What does Genesis 42:38 mean?
Despite Reuben's melodramatic offer (Genesis 42:37), Jacob refuses to risk Benjamin. His response to his sons' news (Genesis 42:29–35) is already bitter and angry (Genesis 42:36). Now, Jacob becomes almost vicious in his reaction. In essence, Jacob decides it is better to count Simeon as lost rather than risk losing his youngest son. Benjamin is the last child of his most beloved wife, Rachel (Genesis 35:16–19). Her other son, Joseph, is believed lost (Genesis 37:32–33).Jacob showed such outrageous favoritism to Joseph that the older brothers became hatefully jealous (Genesis 37:3–4). This led them to sell Joseph into slavery, lying to Jacob about his fate (Genesis 37:28–31). Now, as one of his other sons is being held in Egypt, Jacob refers to Benjamin as "the only one left." This must have been a crushing remark. At best, Jacob means Benjamin is the last of Rachel's children left. And yet, prior history makes it almost certain he means much more than that. In grief and anger, Jacob openly declares his preference for Benjamin, and Joseph, beyond any of his other sons.
For their part, the brothers likely feel more guilt than self-pity. They know they are responsible for what is happening (Genesis 42:21–22). They expressed their conviction that what happened with the Egyptian ruler is God's punishment for their action. In that sense, they are responsible for the loss of Simeon, as well.
Jacob concludes with a statement of grand despair. He felt nearly-fatal grief over the loss of Joseph (Genesis 37:34–35); he is convinced the loss of Benjamin would kill him. The drastic famine will force him to change his plans (Genesis 43:1–2).