At the back is the commandment:
And you shall not stray after your heart
and after your eyes….
This is the mitzvah of guarding one's mind from foreign–i.e., arrogant or lustful–thoughts and desires. These have the negative effect of diverting one's attention from God and confusing his priorities. If one has performed the first five commandments as we have described them, he will naturally strive to protect his precious relationship with God from dissolution.
The Seal of Truth
This commandment is the "seal of truth" (emet) relative to the previous five, the real measure of our relationship with God. The "seal of truth" affirms that all of our pleasure and desire is permeated by the Divine will that we have been attempting to realize as the space encompassing us. The root of "truth" in Hebrew means "loyalty." The "seal of truth" connotes in Kabbalah the sefirah of yesod, which corresponds in the body to the procreative organ, as mentioned above. Here, we are loyal ("true") to our spouse. In our relation to God, our Divine groom, all of our pleasure and desire is permeated by His will and directed to Him alone. "The righteous one is the foundation [yesod] of the world." The righteous one of every generation–"the one [pillar] of the generation"–is as Adam before the sin. Adam was created on the sixth day; he represents God's "seal of truth" with respect to all of creation that preceded. "Truth" is the realization of reaching the end, reaching the purpose of creation–man, the righteous one, the one able to reveal God on earth.
Initially, man is the hidden "unconscious" of all creation, the initial "back" of creation. Adam and Eve were created as Siamese twins, with Eve to the back of Adam. Just as Eve is the initial, unconscious side of Adam, so is Adam, in general (the Torah refers to both Adam and Eve as "Adam"), the initial unconscious of the world, itsraison d'être. Many are the verses of the Torah that speak of serving God by "walking after [‘behind'] Him," alluding to the sixth continuous commandment of the Torah, "and you shall not stray after your hearts and afteryour eyes…." By not straying after, we merit to walk after God in perfect loyalty to Him.
Furthermore, this mitzvah includes the injunction against searching for God in "paths" other than the ways of the Torah. Although these may lure the seeker with the promise of excitement or more immediate spiritual gratification, if he remains true to his ideals, he will focus his mind and heart solely on God as He has made himself "available," so to speak, through the "path" or lifestyle of the Torah. The Torah then teaches us how to properly meet the challenge of finding God in all aspects of reality.
Protecting the Rear
Since the foe prefers to attack from the "rear," i.e., tries to catch one off guard, this commandment is placed "behind" the consciousness, as a protective background force field. Furthermore, "forward" and "backward" are often taken to indicate in Kabbalah "the desired" and "the undesired" (or "less-desired"), respectively. If one performs the first five commandments, he is assured in this sixth that the foreign enticements of this world will truly be "behind him," which is why the verse is phrased "And you shall not stray after [literally, ‘behind'] your heart and after [‘behind'] your eyes."