John Calvin on Genesis 37:30

30. And he returned. We may hence gather that Reuben, under pretense of some other business, stole away from his brethren, that, unknown to them all, he might restore his brother, drawn out of the pit, to his father; and that therefore he was absent at the time when Joseph was sold. And there is no wonder that he was anticipated, when he had taken his course in a different direction from theirs, intending to reach the pit by a circuitous path. But now at length Reuben having lost all hope, unfolds to his brethren the intention which before he dared not confess, lest the boy should be immediately murdered.