Or HaChaim on Genesis 37:29/אור החיים על בראשית ל״ז:כ״ט

1 וישב ראובן אל הבור, Reuben returned to the pit, etc. What was Reuben's argument when he complained to the brothers ואני אנה אני בא, "where shall I go?" Would Joseph not have been lost even if his own suggestion to throw him into a pit had been carried out? After all, the Torah itself testified that Reuben had never told his brothers that he intended to save Joseph and to restore him to his father! When Yehudah said to the other brothers: "what profit is there in killing our brother, etc," does this not prove that Joseph's remaining in the pit was meant to result in his death? How then could Reuben complain to his brothers?

2Actually, Reuben argued that inasmuch as he was the oldest, his father would charge him with leading the search for the missing Joseph from one end of the earth to the other. If Joseph had remained in the pit, he would have brought Joseph's remains to his father and explained to him that wild beasts had killed him. This would have been the end of his involvement. Now he could not do this. This is why he said: "where shall I go?" As a result the brothers hit on the idea of slaughtering a male goat and dipping Joseph's tunic in its blood, etc. By returning the tattered and blood-soaked remains of Joseph's striped coat they made it unnecessary for Reuben to start a search for Joseph.