Genesis 37:29 - Ellicott's Commentary On The Whole Bible

Reuben returned. — Evidently he was not present when Joseph was sold to the Midianites. This has been made into a difficulty, but really it confirms the truth of the narrative. For the difficulty arises solely from the supposition that Joseph’s brethren immediately after casting him into the pit “sat down to eat bread,” an act well described as most cold-blooded. But they were not actually guilty of it; for what the narrative says is that they were having their evening meal when the caravan came in sight. Reuben, between the casting of Joseph into the pit and the evening meal, had apparently gone a long round to fetch in the more distant cattle, and probably had remained away as long as possible, in order to feel sure that his brethren would on his return be at their dinner. He hoped thus to be able to go alone to the cistern, and rescue Joseph, and send him away home before the rest could interfere. Thus rightly understood, it is a proof of the trustworthiness of the history.