Famine strikes the land of Canaan. Isaac heads south towards Egypt, as his father had done in a similar situation. Before Isaac leaves the land, however, God reveals himself to him and commands him not to leave. At this moment, God addresses Isaac, renewing and expanding the covenant that had previously existed with Abraham. After promising that he and his offspring would inherit the land, He explains that it is because Abraham had succeeded in maintaining his end of the covenant. The verse tells us: "Ekev (since) Avraham hearkened to my voice, and kept my ordinations, commandments, laws and teachings" (26:5). There are two points worthy of discussion on this verse.
The first question is on a theological level. Why is it that because of Avraham's awareness of God and his ensuing acts, the covenant should be extended to Isaac? Certainly one can answer that God had indeed promised not just to Avraham but to his offspring. Likewise, one can claim that because God loved Avraham, He decides to extend that love to further generations. These answers would explain why God continues the covenant, but not why God renews the covenant, creating a fresh covenant with Isaac. Perhaps the answer lies in the words of the reason to renew the covenant: due to Avraham's deeds, the covenant will be renewed. Maybe we can suggest that God is telling Isaac: If you continue the deeds of your father, then the covenant will be renewed through you.
The second question is: what are these deeds (i.e. ordinations, commandments, laws and teachings) which are listed in a vague manner? Rashi, based on Chazal's premise that Avraham kept the entire Torah, explains that each word represents categories of the 613 mitzvot contained in the Torah and that Avraham indeed fulfilled the commandments.
Rashbam, clearly disturbed by the assumption that Avraham could have observed commandments not yet given, suggests an answer according to the more straightforward understanding of the text. He claims that some of the terms refer to actual deeds that we find in Avraham's life. Other terms, for Rashbam, are not Torah commandments, as we see them but rather concepts and laws of society which we could say are based on morality: theft, adultery, civil justice, and acts of kindness. He notes that these were all practiced before Sinai and were merely concretized as a national covenant with Israel at Sinai.
Rashbam is teaching us that these deeds contain values and principals of life that relate to the morality and functioning of humanity, and that these precede the Torah. Indeed, these are principals that later become aspects of our divine Torah. Before the Torah, however, these are the deeds that created a society. Avraham succeeded in discovering, even creating a new world following his sense of a divine morality. It was now left to Isaac, to continue this society and develop it further, based on an inner sense of divine morality and social justice.