The difficulty of repenting when the item one has stolen is no longer in the thiefs possession is highlighted in our gemara by referring to the response of the Patriarch Avraham to the offer of the king of Sodom for him to accept the spoils of the war which Avraham had won for him. In his refusal to accept any gift Avraham asked only that no claim be made for payment of the food which his servants had eaten during the course of that war and that his allies, Onair, Eshkol and Mamrei should receive their share of the spoils (Bereishet 14:24). Rabbi Abba saw in Avrahams request regarding the consumed food a source for his statement that "It is difficult to return stolen property which has been consumed, for even great tzaddikim felt themselves incapable of doing so."

Maharsha points out that there was certainly no element of theft involved in Avrahams accepting any of the property of the king of Sodom which he had recovered for him by defeating the superior forces of his enemies. Otherwise Avraham would never have asked for his allies to receive a share of these properties. The reason why there was no aspect of theft is that the king had despaired of ever recovering his property, which made it available to anyone who would undertake an effort for recovery. In addition, the king had on his own initiative waived any claim to this property by offering it all to Avraham.

Avraham, however, in his extraordinary righteousness, refused to accept any gifts and abstained from them as if they were stolen property. To repay what his servants had already eaten, however, was too difficult an undertaking. This serves as a guide to understanding how difficult it is for someone who has committed real theft to do proper repentance regarding stolen property he has already consumed. To demonstrate the practical application of the difficulty in returning stolen property, Maharsha refers us to a gemara (Bava Kama 84b) which tells a story that was the catalyst for an important rabbinical decree. A thief who was seriously considering repenting his ways was discouraged by his wife who warned him that if he made compensation for everything he had stolen he would be left with nothing. When this came to the attention of the Sages they decreed that one should not accept payment from a thief who wishes to repent and no longer has the stolen property in his possession.

When Yosef, the potentate of Egypt whose true identity was still unknown to the brothers who had sold him into slavery, welcomed those brothers upon their return to Egypt together with his younger brother Binyamin, he ordered the official in charge of his household to prepare a lavish meal for himself and his guests.

"Slaughter and prepare" (Bereishet 43:16) is interpreted by this Sage as instructions to show his guests the place in the animal where the slaughtering was performed, and to remove in their presence the gid hanashe (the sinew of the vein on the hollow the thigh). The removal of this latter item was necessary, explains the gemara, according to the opinion of Rabbi Yehuda (Chullin 100b) that the gid hanashe was already forbidden to the descendants of Yaakov from the time that a wound was inflicted on that part of the patriarchs body in his battle with the patron angel of Esav (Bereishet 32:33).

Tosefot raises an interesting question. The gemara concludes that gid hanashe must already have been forbidden based on Yosefs insistence on having it removed to satisfy his brothers kashrut requirements. But is it not possible that even if gid hanashe only became forbidden when the Torah was given, as is the position of the Sages who disagree with Rabbi Yehuda, the sons of Yaakov followed in the path of the Patriarchs and observed the laws which would eventually be given in the Torah? After all, wasnt his concern to show them that a valid slaughtering had been done based on their observance of laws of shechita which were only to be commanded in the Torah?

One of the resolutions offered by Tosefot is that Yosef did not show them the slit throat of the animal to prove that a proper shechita had been performed but rather to show that it had been slain, a step which was required even by Noachide Law which forbids eating the flesh of an animal before it is dead. This approach can be explained with the point made by Ramban in his commentary on Chumash (Bereishet 26:5) that our forefathers observed the commandments which would later appear in the Torah only while in Eretz Yisrael. They could therefore dispense with the need for shechita in Egypt but were obligated to avoid eating the gid hanashe which had already been forbidden. (In regard to whether Noachide Law prohibited eating the flesh of an animal which dies without being slain, see Rashi on the fourth line of Chullin 92b and the commentary of Rabbi Zvi Hirsh Chayot on our gemara.)