The Torah promises in Parashat Ki-Tabo (28:10), "All the nations of the earth will see that the Name of G-d is called upon you, and they will be afraid of you."
Targum Yonatan Ben Uziel explains that this refers to the Tefillin Shel Rosh, which we proudly wear upon our heads. The Torah promises that when the enemies of the Jewish People see the Tefillin on our heads, they will be gripped by fear and will no longer try to inflict harm on us.
How does this work? How will the sight of the Tefillin instill fear within our enemies?
The Kol Aryeh answers this question by developing the symbolic meaning of the Tefillin Shel Rosh.
The Tefillin Shel Rosh features a knot in the back, from which two straps extend along the front of a person's body – one to the right and one to the left. The right side is always associated with Hesed – G-d's kindness, whereas the left side represents Din – judgment. For this reason, it is customary for the right Tefillin strap to extend longer than the left strap, reflecting our desire for an abundance of Hesed.
One who sees the front of a person sees two separate, seemingly disconnected, straps. Outwardly, Hesed and Din are two distinct phenomena. Some events and experiences appear as Hesed, manifestations of G-d's kindness, whereas others seem like pure Din – harsh judgment. However, when the Tefillin Shel Rosh is viewed from the back, it becomes clear that both straps come from the same source, from the knot on the back of the head. The knot of the Tefillin symbolizes the belief that in truth, Hesed and Din are one and the same, that everything Hashem does is for the best, and for our ultimate benefit, even if sometimes it causes us pain. The two "straps" are really one, because everything Hashem does is for the best.
When Moshe was atop Mount Sinai, he asked, "Har'eni Na Et Kebodecha" – "Show me, please, Your glory" (Shemot 33:18). The Sages explained that Moshe wanted to understand the secret of G-d's governance, why the righteous occasionally suffer, whereas the evildoers occasionally enjoy good fortune. G-d responded, "Ve'ra'ita Et Ahorai" – that Moshe would be able to see Him "from the back" (33:23), which the Gemara (Berachot 7) explains to mean that Hashem showed Moshe the knot of His Tefillin. The answer to Moshe's question is the knot of the Tefillin Shel Rosh – the belief that there is no distinction between what we perceive as bad and what we perceive as good. Everything Hashem does is a manifestation of the greatest Hesed, even when we cannot understand how.
This is why Halacha requires reciting Shema while wearing Tefillin. The opening verse of Shema declares, "Hashem Elokenu, Hashem Ehad." The Name of "Havaya" is associated with the attribute of Hesed, whereas the Name "Elokim" refers to divine judgment. The pronouncement "Hashem Elokenu, Hashem Ehad" means that both "Hashem" and "Elokenu" are "Hashe Ehad" – a single manifestation of G-d, an expression of kindness. Even "Elokim" is "Havaya"; even what appears to us as bad is the ultimate good. We must make this pronouncement while wearing our Tefillin – which expresses this fundamental tenet of Emuna (faith).
With this background, we can return to the verse here in Parashat Ki-Tabo.
In the future, the enemy nations will be shown how all the pain and sorrow they caused the Jewish Nation was actually to our benefit, a manifestation of Hashem's kindness. They will see that all their efforts to persecute us and defeat us actually helped us, and in fact led to the final redemption. They will see the "Tefillin Shel Rosh" – that both "straps" are really one, that even the misfortune that Am Yisrael experiences is in fact beneficial for us. And they will thus be overcome by fear and horror, recognizing that all their efforts had the precise opposite effect than they intended, that everything they did to hurt us was in fact helping us.
The message for us is that we must reinforce our steadfast faith in Hashem's unlimited kindness, and repeatedly remind ourselves that "Hashem Elokenu, Hashem Ehad" – even the struggles and hardships of life are to our ultimate benefit. Although we cannot possibly understand in the present moment how this could be good, we must trust that in the future everything will become clear, and we will see with our eyes the "knot of the Tefillin," how everything Hashem did was for the best.