Jamieson, Fausset and Brown on Genesis 42:37

37. Reuben spake, ... Slay my two sons, if I bring him not to thee--This was a thoughtless and unwarrantable condition--one that he never seriously expected his father would accept. It was designed only to give assurance of the greatest care being taken of Benjamin. But unforeseen circumstances might arise to render it impossible for all of them to preserve that young lad (Jas 4:13), and Jacob was much pained by the prospect. Little did he know that God was dealing with him severely, but in kindness (He 12:7, 8), and that all those things he thought against Him were working together for his good.