The Medrash says (Devarim Rabba 4,4) that there is a connection between the last passuk of Parshas Aikev כי אם שמור תשמרון אל כל המצוה הזאת and the first passuk of Parshas Reaih .ראה אנכי נותן לפניכם היום ברכה וקללה The connection between the two parshiyos is the mitzvah of reading the daily Shema and the mitzvah of Shabbos. Let us try to understand where these two mitzvos are hinted in these two pessukim. Secondly, what exactly is the common message which these two passages share together and convey to us.
We suggest the following. Shabbos is derived from the words of כל המצוה which appears as a contradiction. On one hand the word כל is interpreted to mean all, yet the word המצוה refers to one particular known mitzvah? The answer is that כל המצוה is referring to the mitzvah of Shabbos which Chazal tell us is equal to all the 612 remaining mitzvos (Horiyos 8). The Yerushalmi Berachos 9 learns it out from a gezairah shava זכור את יום השבת to למען תזכרו את כל מצוותי as it says:
זכור את יום השבת לקדשו למען תזכרו. רבי אומר זו מצות שבת שהיא שקולה כנגד כל מצותיה של תורה דכתיב ואת שבת קדשך הודעת להם ומצות וחוקים ותורה צוית וגו' להודיעך שהיא שקולה כנגד כל מצותיה של תורה. Shabbos is also hinted to in the second passuk of ראה אנכי נותן לפניכם היום ברכה וקללה The word ראה to see relates to the mitzvah of Shabbos upon where the Torah writes ראו כי ה' נתן לכם השבת (Shmos 16,29). The simple understanding of that passuk is like it says further on that being Shabbos you will not see manna falling from heaven like the rest of the week. Rather you will see in your possession a double portion on Friday. The sefarim however explain the ראו of Shabbos is unique in another way. It is the segulah of Shabbos for one to have more clarity of vision and a deeper perception on the world which brings one to a consciousness of Hashem's presence as the Arugas Habosem writes on this passuk
ואולי הרמז היום על יום השבת, כי ימי חול הם ימי הסתר, ימי קללה. ובשבת מתגלה אורות ודוחה ההסתר וזה ברכה שבת
Shabbos might also have been learned out from the superfluous word היום in the following passuk את הברכה אשר תשמעו אל מצות ה' אלקיכם אשר אנכי מצוה אתכם היום . It already said above ראה אנכי נותן לפניכם היום את הברכה. Therefore one can interpret היום to mean the special day of Shabbos as it says in the parsha of the Manna היום three times referring to Shabbos.
As for the allusion of Kerias Shmah in the words כל המצוה we can say as above that the three parshiyos of Shmah contain 248 words (with either the repeat of ה' אלקיכם אמת or with the addition of אל מלך נאמן when davening privately) corresponding to the 248 positive commandments. So even though מצוה is singular it comes with the כל to convey that the mitzvah of reading the Shma includes one's dedication to align his 248 limbs to the service of Hashem and His mitzvos.
Likewise we can also derive Shma from the first passuk in Reaih specifically from the word אנכי which alludes to the direct Dibbur that emanated from Hashem at Har Sinai אנכי ה' אלקיך which represented the 248 positive mitzvos, in contrast to the Dibbur of לא יהיה לך which alludes to all the 365 negative mitzvos.
In fact the 248 words of Shemah is hinted in the words שמע ישראל ה' אלקינו . What are we supposed to hear? The answer is the Dibbur of Hashem of אנכי ה' אלקיך which emanated directly from Hashem on which the passuk says (Devarim 5,19) קול גדול ולא יסף that Hashem's direct voice never ceased. This means that by reciting the Shma we must try to hear every day the voice of אנכי ה' אלקיך which is the command of שמע to hear exactly this ה' אלקינו and commit ourselves to fulfill the 248 mitzvos with all our limbs. Understandably, this is followed by ה' אחד the end of the Shma passuk which corresponds to the never ending voice of Hashem commanding .לא יהיה אלהים אחרים על פני Hashem is the only deity to serve.
Now let us explain how these two mitzvos of Shabbos and Kerias Shma which are called כל המצוה share in common the necessity of serving Hashem with the drive for excellence in fulfilling all of Hashem's mitzvos rather than just settling to fulfill them with mediocrity. Our theme is based on two Sefornos in the parsha. One is on the first passuk on the words ברכה וקללה.
ראה שאין לעשות עניניו בדרך בינוני כלומר בדרך "פרווע" רק צריך להיות קיצוני דהיינו או ברכה או קללה כלומר כי ברכה יותר מן המספיק עכ"ל.
One is given the choice to side with either blessing or curse. There really is no middle ground for mediocrity. One is incumbent to strive for excellence in his character development, his service to Hashem, and benefiting the world and humanity.
Further on in passuk 30 he reiterates this fundamental.
כדי לפרסם בתחילת כניסתכם שלא תהא ישיבתכם בה על אופן מספיק אבל יהיה על אופן מוצלח או על אופן מקולל עכ"ד.
Your entering Eretz Yisrael should not be driven by the goal of attaining מספיק to live in the land with complacency of religious satisfactoriness.
Therefore the passuk ראה אנכי נותן לפניכם ברכה וקללה tells us that all the mitzvos of Hashem must be fulfilled with לכתחילה, love, fear, kavannah, and uncompromised which takes on the form of מספיק. The reason for this obligation is because Am Yisrael possesses a neshama which is a חלק אלוק ממעל. Hashem is perfect and He in his unfathomable wisdom created a world of perfection and symmetry in the state of beracha. It was man and his wayward desire that ruined the flawless creation which was Hashem's gift to Adam and brought to humanity and to earth curses. As Chazal say in Koheles Rabba 7,18
בשעה שברא הקב"ה את אדם הראשון נטלו והחזירו על כל אילני גן עדן ואמר לו ראה מעשי כמה נאים ומשובחין הן וכל מה שבראתי בשבילך בראתי תן דעתך שלא תקלקל ותחריב את עולמי.
When Hashem created Man he took him for a tour in Gan Eden and said to him look at my creation how pleasant and praiseworthy it is. Pay attention that you should not ruin and destroy my world. When Hashem finished creation the passuk says וירא אלקים את כל אשר עשה והנה טוב מאד. The world was not only good and satisfactory but was incredibly excellent. The Medrash comments on the word מאד that it shares the identical letters of אדם to let us know that Man was created perfectly. Chazal tell us (Yevamos 61 אתם קרויים אדם ( that we exclusively, the Jewish Nation, are called the "Man of creation". It is therefore that the Jewish Nation above any other, must strive not to live merely a life of ordinariness but rather to excel to achieve perfection to the extent that is humanly possible. For by doing so we will thereby imitate Hashem's middah of creation that of טוב מאד.
Therefore by fulfilling all the 613 mitzvos personified in the words כל המצוה especially by keeping the Shabbos which is equal to all 613 mitzvos and reciting every day the Shema properly which corresponds to the 248 positive mitzvos and 365 negative mitzvos, one reaches a shelaimus and perfection. Therefore both Shemiras Shabbos and Kerias Shmah remind a Yid that he should not settle for a partial satisfactory fulfillment of mitzvos but rather seek after shelaimus to excel to the highest level possible. Every day and Shabbos reminds the Yid to upgrade his degree of fulfillment in every mitzvah and tikkun hamidos by pushing the bar always higher increasing the quality and devotion of the mitzvah and middos.
In order to change one's attitude from מספיק to מאד one must first recognize Hashem's מלכות Kingdom in this world and our sole mission which is to enlist all 248 limbs and 365 sinews into the service of Hashem. Avraham Avinu reached such a shelaimus at the Akaidah as the Bnei Yissaschar writes that the malach called out to him אברהם אברהם repeating his name. This repetition indicated that the אברהם on earth who is gematriah 248 was at that moment deeply bonded with his neshama of 248 spiritual limbs in shamayim at its source. Two times אברהם equals מלכות because by completing this last test, he achieved מלכות שמים שלימה. This drive for shelaimus to accept upon oneself the complete bittul to Hashem's malchus is the opposite of דבר מספיק which follows a conduct of life where the service of Hashem is only satisfactory to be "yotzai". That is why you will find that מלכותis the gematriah of דבר מספיק. The clearer the perception and feeling of the presence of Hashem's malchus, the further he leaves a life of מספיק and the closer one comes to perfection.
This is what Rav Yochanan refers to when he says (Rif Berachos 8) הרוצה לקבל עליו עול מלכות שמים שלימה which suggests that there are many madraigos in saying the Shmah which is a demonstration of one's acceptance of the Yoke of Heaven upon himself. Don't exist like a generic Jew on automatic pilot and settle with מספיק surrendering and retiring your soul prematurely by saying I have already reached my limit. Rather, one must continuously strive for shelaimus and perfection in his avodas Hashem by always living his life carrying the banner WORK IN PROGRESS.
Both the recital of Shema and Shemiras Shabbos inspire one to upgrade himself towards a higher spirituality. This is hinted in the passuk שש אנכי על אמרתך כמוצא שלל רב I rejoice with your mitzvos as if I found a grand booty of war (Tehillim 119,162). The words על אמרתך can be referring to the mitzvah of Shabbos. This is hinted in the gematriah of על אמרתך which is 761 the same as .ביום שבת עה"כ Likewise the gematriah of מוצא שלל רב with the three words equals .שבת even though אמרתך is pronounced as plural it is missing a yud which allows itself to be learned as one mitzvah. However according to this mamar we have proven that Shabbos is one mitzvah yet it equals all the mitzvos. In this way a person is zoche to fulfill the mitzvah of Shabbos yet merit simultaneously to draw zechus from all 613 mitzvos. These two mitzvos of Shabbos and Shmah are hinted in the word שש I rejoice, whose acronym is שבת שמע for they bring the spoils of war with them.
Likewise we can darshan שש אנכי to mean that the Dibbur of אנכי was very happy because it contained all the other 247 positive mitzvos.
The Panin Yafos writes that on Shabbos Chazal say that one's speech must be different from the weekdays. In what manner should it manifest itself? He answers for example the first and last three berachos in Shemoneh Esrai on Shaabos which are identical to the weekday, and the same Shema, must be said with more quality on Shabbos. A hint to this interpretation is seen in the gematriah of the first three words of each Parsha of the Shma שמע והיה ויאמר including its letters equal .שבת עה"כ
In Elul we begin to blow shofar as preparation for the shofar of Rosh Hashanah through which we accept upon ourselves the Kingship of Hashem. As Chazal state (Rosh Hashanah 34b) אמלפני מלכויות ובמה בשופר. The word שופר possesses the letters of פשר which means compromise. In business disputes the Torah suggests to compromise. However the shofar of Ellul and Rosh Hashanah are just the opposite of business ethics and that is to accept Hashem's kingdom by ridding ourselves from compromises that come from our choices of מספיק . The Shofar of Rosh Hashanah finds its source in the ram of the Akeidah (Rosh Hashana 16) which Avraham demonstrated by his accepting Hashem's command of shecting Yitzchak which he fulfilled without any compromise and achieved the total recognition and bonding to Hashem's malchus as we brought above.