What does Genesis 42:24 mean?
The ten brothers don't know the man hearing their discussion is Joseph—they only know him as Zaphenath-paneah (Genesis 41:41–45), a powerful vizier of the Egyptian Pharaoh. Joseph's brothers don't know he has understood their recent confession (Genesis 42:21–23). They feel guilty for what they did to him as a boy (Genesis 37:28), ignoring his distress and pleas for help while slave traders carried him away to Egypt. They admit they deserve the treatment they are now receiving (Genesis 42:7–17) because of what they did. Joseph has heard how Reuben stood up to his brothers and tried to stop them.It's no wonder Joseph must turn away and weep. In hindsight, readers may be surprised to see how little Genesis revealed of Joseph's emotional responses before these encounters with his brothers. In this moment, however, there is no disguising his feelings. It must have been intensely meaningful, even healing, for Joseph to hear his brothers' remorse.
Still, he continues with his plan. He will force them to bring his youngest brother Benjamin to him, by holding one of them captive until they do so. He chooses Simeon and ties him up right in front of them. He apparently doesn't want them to imagine that Simeon will be comfortable while they are away.