VaYeshev

"Ruevein returned to the pit, but behold, Yosef was not in the pit. And he tore his clothes [in grief]. He returned to his brothers and said; 'The boy is not here; and I; where can I go?'"

Rashi comments on this pasuk: "Another explanation [of where Reuvein was when Yosef was sold]: He was occupied with his sack-cloth and fasting for having exchanged his father's bed." It seems that there is a connection between Reuvein having moved his father's bed and the act of selling Yosef. What is the connection?

The explanation rests in the fact that there is a better question concerning the selling of Yosef. Here you had a considerable Beis Din - The Asara Shivtei Ka - which judged and ruled that Yosef was obliged the death penalty. There has been no Beis Din as great as them. What then was their sin? A judge can only decide based on what he has seen!

However, there is an even greater wonder pertaining to the selling of Yosef and that is that even though they already ruled that Yosef was obliged the death penalty, why didn't they go as the Gadul HaDor - their Rebbe Yaacov Aveinu! Why didn't they ask? The answer is that there was someone who showed them that you can judge without seeking the opinion of the Sages. You can rule without finding out what the Daas Torah is. This person was Reuvain who decideded he can move his father's bed without asking his Rebbe Yaacov Aveinu. With this he showed them that they can judge without asking. Therefore when Reuvain saw what his action had led to - "he tore his clothes and said "and I; where can I go?"

R' Yosef Dov Soliveitchik as quoted in Sefer Meged Givos Olam by R' Michel Shurkin