Or HaChaim on Genesis 42:21/אור החיים על בראשית מ״ב:כ״א

1 ויאמרו….אבל אשמים אנחנו, They said:…"but we are guilty (of something else)." The word אבל, "but" does not appear to have any meaning here. Onkelos translates it as "truthfully;" I do not agree with this translation either. There was no need for the brothers to say: "truthfully," as if they had so far not spoken truthfully. Besides, why did the brothers have to add: "when we saw his anguish, etc,? All they had to say was that they were guilty of having sold their brother into slavery. This was the essence of their guilt.

2Perhaps they still considered that Joseph had been guilty of the death penalty and if they had only sold him they had actually performed an act of kindness. As to the grief they had caused their father at the time, they were certain that at the present time G'd would not heap further grief upon their father as a result of their having sold Joseph at that time. The only thing they did feel guilty of was not displaying a sense of compassion when they saw Joseph's anguish when he pleaded for his life and they proved cruel. It is not becoming for people who consider themselves as righteous to conduct themselves in such a heartless manner.

3It is also possible that when the brothers saw that they were all being jailed, they began to think which one of them was the cause of the disaster that had befallen them. The common denominator up to that point had been the fact that they had sold Joseph. Since Reuben had been innocent of that crime, not having been present when both the suggestion and the implementation of selling Joseph had been made, they had to search for something that both they and Reuben were guilty of. They concluded therefore that it must have been their heartlessness. Reuben too had not responded to Joseph's pleas as he had suggested that the brothers throw him in the pit instead of killing him outright. No doubt Joseph had pleaded with all the brothers not to do that to him. In fact, slow death in the pit was a more frightening prospect to Joseph than a relatively swift death. The words על כן באה אלינו are an acknowledgement that they all, Reuben included, were guilty of a lack of compassion. Presumably, the brothers must have said these things as soon as they were being led to prison, whereas the Torah reports them as if they had been said after they had all been in prison for three days. Why does the Torah make it appear as if the brothers had only come to this realisation after three days in prison? Presumably, the Torah did not want to diminish the impact Joseph's words and deeds are to make upon the reader. Any diversion would detract us from the clever way Joseph set about creating the scenario he had planned.

4Besides, if we were to assume that the brothers acknowledged their guilt only after they had themselves agreed that Shimon would remain in prison as the hostage, why did it take them so long to acknowledge that Shimon had been more guilty than they?

5Perhaps up to the time when Joseph had said that one of their number had to remain in prison as hostage, they had not related their present experience to the sale of Joseph at all. They had thought that inasmuch as man is a free agent that whatever had happened to them was in retribution for freely committed wrongs. They had not considered what they had done to Joseph as a wrong at all. When Joseph pointedly said: "one of your brothers has to stay here," they suddenly realised that their situation was connected to what they had done to another one of their brothers. The words ויעשו כן then mean that they singled out Shimon. They suddenly realised that the painful experience they now underwent of leaving one of their brothers with a stranger was tit for tat for having abandoned Joseph to a fate with strangers at the time of the sale. I have frequently alluded to the fact that guilt somehow creates situations in which the retribution experienced reminds one of the nature of one's sin. David has mentioned this in Psalms 62,13: כי אתה תשלם לאיש כמעשהו, "for You repay each man according to his deeds." The brothers saying אבל may therefore be understood thus: "If our present experience had been even slightly different we would not have realised why we are now being punished; but the very fact that our punishment corresponds to the nature of our sin convinces us of our guilt. Now we are absolutely certain that we are guilty of lack of compassion."

6The very fact that it was Shimon who was being detained convinced them; after all, according to Tanchuma Parshat Vayechi, it had been Shimon who had made the suggestion to kill Joseph; he and Levi were the subject of 37,19 "one said to his brother." Shimon the elder said to his brother Levi the younger. They had been a team already when they wiped out the men in the city of Shechem.