Or HaChaim on Genesis 42:2/אור החיים על בראשית מ״ב:ב׳

1 ונחיה ולא נמות. "so that we shall live and not die." The reason that Jacob repeated "so that we shall not die," was that negligence would be a capital sin for which an accounting would have to be given even in the Hereafter. On the other hand, if they made appropriate efforts to secure a supply of food, their lives in this world as well as in the Hereafter would be assured.

2The verse might also be read thus: ונחיה, "so that we may live comfortably," ולא נמות "or at least not die." It would all depend on the amount they were able to buy in Egypt.