Sforno on Genesis 42:37/ספורנו על בראשית מ״ב:ל״ז

1את שני בני תמית, he cursed (conditionally) now two of his sons that they should die if he would not bring back Binyamin safely. The matter is similar to an incident related in Shabbat 108 where Rav said to Shemuel “may it be G’d’s will …that your children will not live.” The curse came true. [The story is extremely enigmatic, seeing that Rav who had thought that Shemuel had treated him not only in a miserly fashion, but had caused him physical discomfort deliberately, had become aware in good time that Shemuel, an outstanding physician, had done what he did in order to relieve an ailment Rav had clearly been suffering from. In spite of this, the conditional curse was fulfilled, much as Yaakov who had cursed the thief who had stolen Lavan’s teraphim not knowing that it had been Rachel. Although the condition had been that if the thief would be found he should not live, Rachel died in spite of the thief (she herself) never having been found. Ed.]