Musar zu Bereschit 26:4

We need to appreciate that the name יעקב is in fact ישראל. The name יעקב alludes to an exalted position on earth, i.e. in this world; it reflects observance of Torah in this world, not expecting to be rewarded in this world, but being content היום, לעשותו, מחל לקבל שכרם, as we have explained earlier. The name ישראל is the direct outcome of יעקב having been what he was here on earth. Our sages have taught us that שכר מצוה מצוה, that the reward of performing a commandment is the מצוה itself (Avot 4,2). This means that the spiritual element of the מצוה one performs on earth becomes the glue with which one attaches oneself to G–d in the Hereafter. When David refers to the great reward in store as a result of observing the commandments, i.e. בשמרם עקב רב (Psalms 19,12), he points to the seemingly insignificant commandments people are in the habit of ignoring. The word Eikev means סוף, end. The word סוף also means תכלית, the ultimate purpose of life as defined by Solomon in Kohelet 12,13 in the words: סוף דבר את האלוקים ירא ואת מצותיו שמור כי זה כל האדם. "To sum up: Fear the Lord, observe His commandments, for this is what man is all about." This סוף which Solomon speaks about in Kohelet is the latter part of Jacob's name עקב, heel, itself the tail-end of a person. This יעקב was alluded to earlier in the Torah when G–d said to Isaacs, “I shall multiply your seed like the stars of the heaven" (26,4). G–d goes on to say that inheritance of the land of Israel will be due to Abraham having listened to G–d's voice and having observed His commandments, עקב אשר שמע אברהם בקולי. The word עקב refers to that part of יעקב's name.