36 And Jacob their father said unto them, Me have ye bereaved of my children: Joseph is not, and Simeon is not, and ye will take Benjamin away: all these things are against me. 37 And Reuben spake unto his father, saying, Slay my two sons, if I bring him not to thee: deliver him into my hand, and I will bring him to thee again. 38 And he said, My son shall not go down with you; for his brother is dead, and he is left alone: if mischief befall him by the way in the which ye go, then shall ye bring down my gray hairs with sorrow to the grave.
It seems that Reuben was in favor of immediately returning to Egypt, proving that their youngest brother existed, and getting Simeon out of bondage. But this was a risk too great for Jacob. He had lost one son, and now a second, and he would rather cut his losses here than risk losing a third!
Reuben still contends the matter, though. Simeon is Reuben’s blood brother, both being the sons of Leah. Simeon was also the very next son born after Reuben, the nearest to him of all his brethren. Thus, of all his brothers, Simeon might be the one that Reuben has the most motivation to get free.
Perhaps the brothers had evil intentions towards Joseph in the past, but Reuben makes it clear that he harbors no such ill will for Benjamin. He is willing to put his own sons on the line, committing them to death if he doesn’t keep his promise and bring Benjamin back safe and sound! With such an oath we can be sure he truly intended to let no harm come to the boy.
And in Reuben’s oath there seems to be a messianic representation. A father is willing to put the life of his own son on the line in order to save another child. It is a moving offer, yet it is not enough to sway Jacob. For even if Reuben’s heart is in the right place, and he will not personally cause harm to Benjamin, he cannot claim to have power over all the other factors in the world. He could really try his best to preserve his younger brother, but mischief might still “befall him by the way.”