והיה עקב תשמעון את המשפטים האלה ושמרתם ועשיתם אתם ושמר ה' אלקיך לך את הברית ואת החסד אשר נשבע לאבותך
And, the result will be, when you adhere to these laws and do them, Hashem your G-d will keep the covenant and the kindness which he swore to your Forefathers.
The word עקב is expounded upon in the Midrash Tanchuma: The meaning of the word עקב ,literally "heel", refers to the Mitzvot that a person belittles, treds upon, as it were, with his heel – for these mitzvoth the reward is great as for other mitzvoth which are considered of paramount importance. As mentioned in Psalms, בשמרם עקב רב , reward is reserved for those who keep the small mitzvoth.
R' Ben Tzion Mutsafi expounds on this. In the army, a soldier is obliged to have his face cleanly shaved, shirt tucked in, boots tied, and hair cut short. Paying attention to these little things, the things that people take for granted, is often the criterion being judged as obedient. These seemingly minute details put one into a state of mind and make one subconsciously acknowledge the authority of whoever demands them. And, our state of mind determines the quality and fervor of how we do things.
Coming to shul early enough to say what we need to say, without catching up. Not speaking in shul. Praying from the siddur. These things, although they seem to have only secondary importance, things that are not as great as the Amidah itself or as great as the Kriat Shema, will make the whole difference in the quality of our Amidah and Kriat Shema . ….The things that we step on: the open cell phone during prayers...The way we dress when we come to shul.
This is true in regard to the Mitzvah of Shabbat. ממצוא חפציך ודבר דבר - in the words we say before Kiddush Shabbat day, we mention the law of the Prophets that we refrain from "speaking speech that refers to things that are forbidden on Shabbat." This law, says R' Mutsafi, is a law that many "step on with their heel." The more careful we are in keeping this law, the more seriousness we will relate to our adherence to the 39 Melachot that are forbidden from the Torah as well.
The Midrash Hagadol focuses on the words ושמרתם ועשיתם : the words that mean, literally, to keep and observe. The word שמור refers to keeping the Mitzvot. Keeping, or watching means to preparing yourself for and awaiting the opportunity to do the mitzvah. Be ready for it before it comes, and when it comes, do it in the most beautiful and praiseworthy way possible. Accept and welcome the Shabbat early. Be among the first in shul awaiting a minyan. Although in the world we know, a worker will not receive any special payment from his boss for coming early and waiting for his job to begin, this is not true in regard to our reward for Mitzvot. We are rewarded for being ready ahead of time. This behavior can be observed in old-timers. We tend to think that they are ready early to perform a mitzvah because they do not have that many things to do. The truth is that this was how things were in the last generation. Coming to shul early, awaiting prayers was a value that was widespread, understood and respected.
If we look closely at the prayer that is cited at a Siyum of a tractate in Shas, we will notice an interesting statement : ...אנו רצים והם רצים We run and they run. . . When it comes to getting paid as a worker, the boss does not care if you came by foot and it took you a couple of hours, just be there on time! With doing a mitzvah it is not that way. The effort put in in order to get you to the Mitzvah is reckoned in with precision: How far is shul from your house? - One gets rewarded for every step he takes along the way. Let us remember that the "heel", is what might make the whole difference of what type of World we have waiting for us.