וַיֹּאמֶר אֱלֹהִים אֶל מֹשֶׁה אֶהְיֶה אֲשֶׁר אֶהְיֶה
God said to Moshe, “I Shall Be As I Shall Be.” (3:14)
In response to Moshe’s question at the Burning Bush, “When Bnei Yisrael ask me Your Name, what shall I say?” Hashem responds that His Name is “אהיה אשר אהיה,” which translates literally as “I Shall Be As I Shall Be.” Needless to say, the meaning and significance of this Name, as well as its relevance to the Exodus from Egypt, can be understood on many levels.
The Meshech Chochmah discusses an aspect of this Name which emerges from the gematria (numerical value) of the word “אהיה,” which is twenty-one. When the word is repeated in this Name – “אהיה אשר אהיה” – the combined numerical value is forty-two. As discussed in the Gemara, one of the holiest Names of Hashem is the Name which contains forty-two letters. The Gemara there states that anyone who “knows” this Name will have his awe cast over those around him. It is to this Name of forty-two letters that the Name “אהיה אשר אהיה” alludes.
This association immediately raises a couple of questions:
• What is the meaning behind one Name of Hashem alluding to another? • Why, in the Name as it appears in the form of “אהיה אשר אהיה” is forty-two broken up into two units of twenty-one?
Hashem’s Name and The Two Types of Tefillin
The Meshech Chochmah explains. The two sets of twenty-one have yet another parallel, for the parshiyos inside the tefillin contain twenty-one mentions of Hashem’s Name. Since the tefillin themselves are comprised of two units – the shel yad (on the arm) and the shel rosh (on the head) – the total number of mentions of Hashem’s Name in the tefillin is forty-two. This means that the two tefillin together represent in some form the Divine Name of forty-two letters. Indeed, adds the Meshech Chochmah, the Rambam makes a point of specifying that both the arm tefillin and head tefillin contain twenty-one Names of Hashem, and is also alluding thereby to their combined significance in representing the Name of forty-two letters.
This is still somewhat obscure. How do the two types of tefillin correspond to the Name of Hashem which consists of forty-two letters?
The mitzva of tefillin represents our connection with Hashem. We bind them to our arm and head as an expression of the way we are bound to Him. In this light, the Gemara informs us that Hashem also has tefillin, for they in turn represent His connection with us. Thus, as the Gemara explains, whereas our tefillin have the parshiyos of “Shema Yisrael etc.” which express our acceptance of Hashem as our King, Hashem’s tefillin contain the pasuk “וּמִי כְּעַמְּךָ יִשְׂרָאֵל גּוֹי אֶחָד בָּאָרֶץ – And who is like Your People Yisrael, a unique nation in the world,” which expresses His special relationship with the Jewish People.
This connection itself can express itself in one of two forms. Sometimes, Hashem’s supervision of His People is manifest and revealed for all to see, whether in the form of open miracles or of stunning manipulation of natural events. At other times, his protection is more concealed, allowing for the continued existence of the Jewish People against all odds, but not expressing itself in any measure beyond that. These two forms of supervision correspond to the two types of tefillin. The tefillin shel rosh are meant to be noticeable upon the person’s head, while the tefillin shel yad are more concealed, as the Gemara expounds concerning them, “והיה לך לאות – ולא לאחרים לאות – It shall be a sign for you – and not a sign for others.” In terms of our discussion we understand that revealed Providence corresponds to the tefillin shel rosh, while concealed Providence corresponds to the tefillin shel yad.
This is the meaning of the statement that one who knows the Name of forty-two letters will have his awe cast on his surroundings. For a person to “know” the Name of forty-two letters means to have achieved a level where Hashem’s supervision of that person is manifest for all to see. That is what leads to the awe which is cast on those who encounter him. Indeed, this will give us deeper insight into a parallel statement said regarding tefillin themselves. Commenting on the pasuk “וְרָאוּ כָּל עַמֵּי הָאָרֶץ כִּי שֵׁם ה' נִקְרָא עָלֶיךָ וְיָרְאוּ מִמֶּךָּ – All the nations of the land will see that Hashem’s Name is called upon you, and they will be in awe of you,” R’ Eliezer states, “אלו תפילין שבראש – This refers to the tefillin on one’s head.” This means that when Hashem’s Divine protection of the Jewish People is clearly manifest – as represented by the tefillin shel rosh – this will generate awe on the part of all those who behold it. The halachah states that the tefillin shel rosh can only be worn together with the tefillin shel yad, which means that the shel rosh represents the Name of forty-two letters, the product of its twenty-one Names of Hashem together with the twenty-one Names in the shel yad which is always worn together with it.
This, then, is the significance of splitting up the Name of forty-two into two units of twenty-one, as expressed in the Name “אהיה אשר אהיה,” for the Name of forty-two is itself a product of two types of Divine connection, each represented by the twenty-one Names in the tefillin. There are times when only one of these forms of connection is in operation, that is, when hashgachah is concealed. Therefore, as a prelude to the stunning series of miracles which will culminate in the Exodus from Egypt, Hashem informs Moshe that the Name which characterizes this period is “אהיה אשר אהיה,” for Hashem’s “shel rosh” connection with His People will be visible for all to see.
From Torah to Nevi’im
Resonance of the connection between Hashem’s hashgacha and the two types of tefillin can be observed later on in Tanach as well. When Shlomo HaMelech has finished building the Beis Hamikdash, Hashem appears to him and says:
הִקְדַּשְׁתִּי אֶת הַבַּיִת הַזֶּה אֲשֶׁר בָּנִיתָה לָשׂוּם שְׁמִי שָׁם עַד עוֹלָם וְהָיוּ עֵינַי וְלִבִּי שָׁם כָּל הַיָּמִים
I have sanctified this House that you have built, to place My Name there forever, and My eyes and My heart shall be there all the days.
With these words, Hashem is informing Shlomo that the Shechinah will never depart from the site of the Beis Hamikdash – even if it should be destroyed. However, the level on which the Shechinah will be manifest will differ depending on whether or not the Beis Hamikdash itself is standing. Therefore, Hashem first states that His Name will be “placed there forever,” i.e. even during the period of destruction and exile, the Shechinah will not depart. However, Hashem’s presence there will only be revealed – through the miracles which accompany the ongoing function of the Beis Hamikdash – when the Jewish People are in a state of redemption and the Beis Hamikdash itself is standing. This revealed level of hashgachah is represented by the “eyes” and the “heart”, for the shel rosh is described by the pasuk as being placed “between your eyes,” while the shel yad is placed “by your heart”.  Thus, Hashem states that His “eyes and heart” – representing revealed hashgachah – will be there specifically at the times represented by “day”, i.e. when Bnei Yisrael are in a redeemed state and not when they are in exile as represented by “night”.
From Nevi’im to Chazal
This idea will also provide us with some insight into a rather enigmatic exchange recorded by the Gemara  which took place between R’ Yehoshua ben Chananiah and a certain heretic, in the presence of the local Roman governor. The Gemara relates that the heretic made a display of covering his face, indicating that Hashem had hidden His face from the Jewish People. In response to this, R’ Yehoshua held out his arm. How is this a response to the heretic’s gesture?
What R’ Yehoshua was saying is that even if Hashem’s face is hidden from the Jewish people, represented by the lack of revealed hashgacha reflected in the shel rosh, that does not mean His connection with them is fundamentally terminated. It continues in the concealed form of the shel yad, guiding and preserving them throughout history until they merit once again for all to see that Hashem’s Name is called upon them through both types of connection represented by the shel yad and shel rosh – “אהיה אשר אהיה”! 
 Kiddushin 71a.
 Hilchos Tefillin 4:14.
 Berachos 6a.
 Divrei Hayamim-1, 17:21.
 Menachos 37b.
 Devarim 28:10.
 Berachos 6a.
 See Menachos 36a.
 Melachim-1, 9:3.
 Devarim 6:8.
 Ibid., 11:18.
 Chagigah 5b.
 Perhaps this idea can also give us further insight into the concluding words of our pasuk, “וַיֹּאמֶר כֹּה תֹאמַר לִבְנֵי יִשְׂרָאֵל אֶהְיֶה שְׁלָחַנִי אֲלֵיכֶם – He said, thus you shall say to the Children of Israel, ‘I Shall Be’ sent me to you”. Once Hashem has revealed that He will be orchestrating the Exodus through the Name “אהיה אשר אהיה,” why does He then conclude by saying that Moshe should inform Bnei Yisrael that “אהיה” sent him to them? The Ramban (end of Parshas Bo) writes that the goal of all the open miracles with which Hashem brought about the Exodus was in order for Bnei Yisrael to learn therefrom that His guidance always accompanies them in the form of hidden miracles. The halachah quoted above, that the shel rosh is only ever worn together with the shel yad, teaches us that although one may only be able to see the shel rosh, he can infer thereby the presence of the shel yad as well. Similarly, our reaction to Hashem’s “shel rosh”, i.e. open, guidance should be to infer the existence of the “shel yad” guidance, even if it is concealed. Thus, the full message to Bnei Yisrael prior to their redemption is that the open hashgacha which they are about to experience – “אהיה אשר אהיה” – is coming from the One Who has in fact been with them throughout their tribulations in Egypt, guiding them through concealed hashgacha to ensure their survival in spite of their oppressor’s oppressive and destructive designs – “אהיה שלחני אליכם”!