For your servant became a pledge of safety for the boy to my father, saying, 'If I do not bring him back to you, then I shall bear the blame before my father all my life.' Now therefore, please let your servant remain instead of the boy as a servant to my lord, and let the boy go back with his brothers. For how can I go back to my father if the boy is not with me? I fear to see the evil that would find my father.
Changed hearts are seen in Judah's appeal. The ESV Study Bible describes the change succinctly:
"Building on what he has already said, Judah petitions Joseph to let Benjamin return to his father in Canaan in order to prevent him from dying of grief at the loss of a second son. To make this possible, Judah offers to take Benjamin's place and become Joseph's slave (Gen. 44:33). For Judah, this would be preferable to witnessing his father's distress if Benjamin remained in Egypt (Gen. 44:34). The selfless attitude of Judah stands in sharp contrast to what he previously displayed when arguing that Joseph should be sold into slavery (see Genesis 37:26-27). On that occasion, Judah cared little about the impact that this would have on his father."
God has used the plans of Joseph to test his brothers in such a way as to prove their character and convince Joseph that there was real change that had gone on in them since his separation from him. Witnessing Judah's appeal made Joseph aware of what was happening in the mean hearts of his brothers. They had changed. The biggest evidence has to do with their relationship with Israel, their father. They had little regard for how Joseph's faked death would affect him. In fact, part of what they did in selling Joseph into slavery was meant to get back at their father's partiality to him. But know, as they have lived with their father's grief over many years, they are hurting for the old man. Judah's intervention and offer of himself in Benjamin's place shows that they had grown to care for their family, their father, and his feelings.
This represented everything that Joseph longed to see in them. And it will set the scene for what will occur in the final chapters of Genesis, where a happy family reunion is made. It is that sort of real-life drama that makes this book so interesting and compelling to read. It is rooted in who people are as they relate to God and one another. And the tale of Joseph is a wonderful and rich tapestry of human experience.