Another reason for the Torah's careful delineation of Avraham's fulfillment of the mitzvah of hospitality is to teach the concept of "The actions of the fathers are a sign for the children." Everything that Avraham did to serve his guests was taken into account by G-d, so that He could reward the Jewish people at a later date - during their trek through the desert. Thus, because Avraham gave his guests water, the Jewish people would be given a well. Because Avraham gave them bread, his descendants would be given manna. And because Avraham served his guests meat, G-d would repay Bnei Yisrael with Slav (meat).

We see the same idea with reference to "Akeidas Yitzchak" later in the parasha. We are told that Avraham "split the wood for the offering." G-d would later reward Avraham for this by splitting the sea for the Jewish people. Were it not for this act by Avraham, perhaps this miracle would not have occurred. Indeed, the midrash informs us that upon being commanded by G-d to split, the sea "argued", claiming that the Jewish people had themselves fallen prey to idolatry and were no more deserving of salvation than their Egyptian counterparts. It did not realize that it was being told to split in the merit of Avraham. Indeed, what seemed an insignificant act many years earlier, greatly impacted the course of Jewish history.

Once it is understood that Avraham's actions in these two instances is to teach the concept of "The actions of the fathers are a signpost for the children", one can still ask why such is the case with these two events in particular. Were there not numerous other events in the life of Avraham which could have served the same purpose?

Whether it is in this world or the next, it is well known that one is always rewarded for any mitzvah that he performs. It is not as well known, however, that such may be the case even when does not succeed in his efforts to perform a mitzvah.

These two incidents represent situations where Avraham was actually unsuccessful in fulfilling G-d command. Avraham thought he was serving guests, but in truth, since the guests were angels who had no need for food or drink (see Rashi), there was in fact no mitzvah to serve them. Avraham attempted to offer his son Yitzchak as a sacrifice, but at the last moment, G-d stopped him from doing so. Yet so great is the chesed of G-d that this ultimately does not matter. He considered Avraham's efforts alone, rather than their outcome, to be great enough that he would still reward Bnei Yisrael on his behalf upon their exodus from Egypt.