This week's parshah features the first Tochacha (Admonition). The Tochacha invokes punishment for those who abandon the Torah, and the failure of Bnei Yisroel to observe the Shmittah (the Sabbatical Year) is presented as a major factor in bringing about this punishment. In fact, the Tochacha notes three times the neglect to observe Shmittah (26:34, 35, 43). Why is Shmittah given so much focus in the Tochacha?
The major theme of Shmittah is recognition of God's hand behind nature (Sefer Ha-Chinuch m. 84). Although the farmer toils and reaps the apparent work of his hands, Shmittah tells us to take a step back and realize that all comes from Hashem, not from Man or nature. God's complete control and sovereignty are affirmed, and that is why Shmittah is referred to and compared with Shabbos. (Vayikra 25:3 et al.)
The Tochacha contains the repeated refrain , "vahalachtem imi b'keri" - "if you act happenstance with Me" - indicating an unawareness of God's hand in one's life. When one behaves as if life runs on automatic pilot or with no control system at all, he denies the very message of Shmittah, that the natural order, seemingly under the control of Man or no one at all, is really directed totally by Hashem. Thus, the Tochacha is the Torah's direct reply for failure to adhere to the message of Shmittah.
For these reasons, it is no coincidence that the Tochacha is formed in groups of multiple sevens, for it is a parallel to Shmittah, which is counted in series of sevens. So, too, the Tochacha ends with exile and the desolation of Eretz Yisroel, for its punishment is an unraveling of the life depicted by those who keep Shmittah. Rather than living in the Land after conquest and being part of its development and flourishing bounty, all is reversed, with the Land being abandoned and fallow.
Chazal note that the root of the sins that bring upon the punishments of the Tochacha is failure to toil in Torah [being "ameilim b'Torah"]. (Toras Kohanim 1:2, 2:1, in Rashi on 26:14) Toiling in Torah is more than merely observing Torah, and it is more than even learning Torah with regularity. Being "ameilim b'Torah" means that one's effort and focus is on Torah; one is aggressive and is "moser nefesh" - sacrifices - to learn Torah and immerse himself in it to the greatest depth possible. What does toiling in Torah have to do with Shmittah and abandoning Torah altogether? The answer is that being "ameilim b'Torah" means that Torah is a person's priority, that the Word of God is in his mind, that he is conscious of God's kedusha throughout his days and life. This is the message of Shmittah, to be aware of God's Presence and interaction, rather than going on with life devoid of such thoughts. One must mentally connect to Hashem throughout, and focus and immersion in Torah is the embodiment of this goal. (This is why Parshas Behar concludes with the prohibitions of making forbidden images and bowing on a hewn stone floor outside the Beis Ha-Mikdash ["Even Maskis"], and why the Torah then proclaims, "You shall keep my Shabbosos and be in awe of my Mikdash, I am God" (26:1-2) right after the full treatment of Shmittah and Eved Ivri (Jewish servant). The concluding verses of Behar seem totally out of place, but they are there to state that rather than distancing oneself from Hashem by selling himself as an Eved Ivri, thereby being bound to a human master and exempt from many mitzvos, one must cling directly to God, similar to the need to keep focus on the Beis Ha-Mikdash and observe Shabbos, which affirm God's Presence and control, rather than going stray after foreign images and bowing in formats that counter the uniqueness of the Beis Ha-Mikdash.
One needs to actively and passionately focus on Hashem and being under His watch. This is the message of Shmittah and the Tochacha.
On another level, we need to ask why the Tochacha is at the end of Sefer Vayikra. There are many possible answers. (See Archive; click below.) Sefer Vayikra is almost entirely devoted to "rituals": Avodah in the Mikdash, Tumah and Tahara, Tzara'as, Shmittah and Yovel, etc. Perhaps the Torah places the Tochacha at the conclusion of Yayikra to tell us that one cannot get lost in the technical rituals and lose sight of Hashem. We must observe every iota of the Torah because Hashem commanded it as such. However, to observe the mitzvos and not be cognizant of the One behind the mitzvos is pure distortion of Torah and hypocrisy. This is why Shmittah and the Tochacha come at the conclusion of Sefer Vayikra, as they charge us to remain focused on Hashem and be aware of His Presence in our lives; for mere rote observance of God's commands does not suffice. One must relate to Hashem as seek to bask in His kedushah, be aware of His involvement in life and our connection to Him.
For a full library of divrei Torah, please see TorahHeights.com