Adam Clarke on Genesis 37:21

Reuben heard it - Though Reuben appears to have been a transgressor of no ordinary magnitude, if we take Gen 35:22 according to the letter, yet his bosom was not the habitation of cruelly. He determined, if possible, to save his brother from death, and deliver him safely to his father, with whose fondness for him he was sufficiently acquainted. Josephus, in his usual way, puts a long flourishing speech in the mouth of Reuben on the occasion, spoken in order to dissuade his brethren from their barbarous purpose; but as it is totally unfounded, it is worthy of no regard.