Years pass, and Joseph's brothers come to him in Egypt to buy grain during the famine. It's important to realize that although the people of Egypt have been storing up grain for just this purpose for years, it's not free to anyone when the time comes to need it; everyone has to pay for their fair share, even if they contributed it to the storage in the first place.
When Joseph's brothers come, they leave their youngest brother at home. This is because he has become his father, Jacob's, treasured possession; he's the only remaining son from the beloved Rachel, who died in childbirth with Benjamin. But Joseph knows there is another brother, his closest brother, and he longs to see him.
So he sends his brothers back with their grain and their money and tells them, in no uncertain terms, that if they come back even one more time, their youngest brother must come with them or they won't get anywhere near him or his grain. This sends a panic among the brothers, who know that there's no way they can ask their father, Jacob, to send Benjamin with them.
In order to understand what happens next, we have to remember what happened before, when the brothers plotted to kill Joseph, then decided to sell him into slavery instead. Remember that it was Reuben who secretly tried to salvage Joseph's life, who begged for him to be buried in a dry cistern with the plan to come back and rescue him later.
And it is Reuben who steps forward first here. The eldest of all sons. He tells his father that he will take responsibility for the boy, Benjamin. He guarantees his safe return. He in no uncertain terms promises that they will all come back, and if Benjamin doesn't come back, Jacob can take it out on him. He's willing to make that deal.
But Jacob, it seems, is not. Because nothing happens when Reuben speaks his deal. Nothing. The sons do not return to Egypt then. They do not go in search of more grain. Nothing.
It is only when the grain runs out, when they have no choice but to go back to Egypt, that the same deal is offered to Jacob for the safety of Benjamin. But this time, it's not Reuben, the firstborn, the eldest son who had tried to save Joseph's life that fateful day....
That's right. It's the same Judah whose devious plan was to sell Joseph away and tear his coat and cover it in blood. It's the same Judah who broke his father's heart the first time. It's the same Judah who unwittingly set all this up, but who has carried with him the guilt (we assume) of what he's done to Joseph for all of these years. And it's Judah's offer that Jacob accepts. The brothers return to Egypt with Judah held accountable for Rachel's other son.
It's one of those interesting Bible things that's easy to miss, but how rich it is when we see it. How beautiful.