The greatness and severity of the Mitzvah of Tefillin:
The reward for the Mitzvah of Tefillin is very great. The following statements are recorded by Admur and Chazal regarding the greatness and importance of this Mitzvah:
A. Karkafta-Poshei Yisrael Begufan:
One who does not put on Tefillin [for even one day] is considered within the category of “Posheiy Yisrael Begufan.” [Such a person is called a Karkafta, and according to Kabbalah does not merit to be resurrected in the period of Techias Hameisim. This Talmudic dictum served as one of the many reasons behind why the Rebbe specifically chose the Mitzvah of Tefillin for his Mivtza campaign which he began just days before the six day war, as the Mitzvah of Tefillin has a special severity of the status of Karkafta.] Even if he refrains from wearing them due to fear of not keeping a clean body, he has transgressed, as certainly he is easily able to guard his body during the time of Shema and Shemoneh Esrei. [Nevertheless, in such a case, some Poskim rule the person is not called a Posheia if he does not wear the Tefillin due to reasons of cleanliness.]
B. The Mitzvah of Tefillin is the deciding factor on judgment day:
The Sages taught that on the Day of Judgment, if one is [judged] meritorious in the Mitzvah of Tefillin then the side of merit dominates. However, if one was negligent in the Mitzvah then the side of liability dominates.
C. Is the greatest positive command:
The Mitzvah of Tefillin is the greatest positive Mitzvah in the entire Torah, as the entire Torah is connected to Tefillin. For this reason, every person needs to be careful in the Mitzvah of Tefillin.
D. Merits one long life:
All those who are careful in the Mitzvah of Tefillin will have lengthy days. [This is because the Tefillin correspond to the heart and mind onto which one’s life depends. Some say that one is to state this Talmudic passage prior to wearing the Tefillin and that doing so is a Segula for long life.]
Sparks of Chassidus:
What is the meaning behind the word Tefillin?
The word Tefillin comes from the word Pelila/Testimony, as the Tefillin are a testimony that the Divine presence dwells upon us. Alternatively, the term Tefillin comes from the word Haflah which means unique, as the Jewish people are unique from amongst the nations. Alternatively, it comes from the word “Thought,” such as in the verse “Reos Panecha Lo Pilalti,” coming to teach us that one may not remove his mind from the Tefillin.
The two witnesses that testifies to a Jew’s identity:
Every Jew is required daily to have 2 signs which show that he is Jewish, as is a law regarding all testimony that one requires 2 witnesses. On a normal weekday, these 2 signs are the sign of the Bris Milah, and the sign of the Tefillin. On Shabbos and Yom Tov, the 2 signs are the sign of the Bris Milah, and the sign of Shabbos or Yom Tov. One who G-d forbid does not put on Tefillin even one day, loses his valid testimony for that day, and he is not considered a complete Jew unless he has these 2 witnesses.
Testimony of Shechina:
The Tefillin serve as a testimony that the Shechina resides on the Jewish people. The Shelah Hakadosh states as follows: After the destruction of Temple the Shechina continues to reside on the Jewish people in merit of the Tefillin. This is based on the Zohar which states that through wearing the Tefillin one fulfills the verse of “Make me a Mikdash and I will dwell on them.” The Tefillin which are worn on the person are similar to the Cherubim of the Aron Habris onto which the Divine presence rested.
The Kabbalistic correspondence:
The four compartments of the Tefillin Shel Rosh correspond to the four Mochin of Z”a. This means that through wearing the Tefillin one draws down Mochin of Z”a.
The head of all the Mitzvos-The uniqueness of Tefillin over other Mitzvos:
Chazal state that the Mitzvah of Tefillin is connected to the entire Torah. The purpose of all the Torah and Mitzvos is to draw G-d’s unity down into the lower worlds. Although this is accomplished through fulfilling all Mitzvos, nevertheless, by the Mitzvah of Tefillin this is more revealed, as the Parshiyos inside the Tefillin discuss G-d’s unity. Hence it is the head of all the Mitzvos.
Hashem considers one who wears Tefillin to be learning Torah day and night:
Rebbe Eliezer stated: The Jewish people said before Hashem that they would really like to study Torah day and night but they simply do not have the time to do so. Hakadosh Baruch Hu replied to them that they should fulfill the Mitzvah of Tefillin and He will consider it as if they are toiling in Torah learning day and night. Thus, we see that the greatness of putting on Tefillin is equal to that of studying Torah. [This Midrashic statement serves as the foundation of the famous Chassidic discourse “Isa Bemidrash Tehillin,” which is customarily recited from memory by the Bar Mitzvah boy. In this discourse, the Rebbe Rayatz relates the following: How indeed is it possible to say that the simple Mitzvah of putting on Tefillin for a short part of the day is equal to the study of Torah by day and night? The explanation however is that in truth they are similar in their effect. The effect of Torah learning is that it draws down Mochin from the level of Chochmah into the level of Midos, known as Z”a. Now, when a Jew puts on Tefillin it causes that Hashem likewise puts on Tefillin. This is explained to mean that the level of Kudsha Berich Hu, which is Z”a, has Mochin drawn down into it, as explained next. This is the exact effect that is caused by Torah learning. Nonetheless, even so, the wearing of Tefillin does not take the place of Torah learning, and it is just that it counts in its stead if one does not have the time to learn.]
Hashem wears Tefillin-The Kabalistic meaning:
Chazal state that Hashem wears Tefillin, in which it states “Mi Keamecha Keyisrael Goy Echad Ba’aretz.” There are two Kabbalistic explanations behind this statement: 1) This means that the level called Hakadosh Baruch Hu, which is Z”a, wears Tefillin and draws down the level of Mochin from Chochmah and Bina to Z”a. However, in the level of Keser, the wearing of Tefillin is irrelevant. 2) This means that the level called Hakadosh Baruch Hu, which is Keser, wears Tefillin and draws down the level of Mochin from above Keser into Keser. Once the Tefillin have been prepared for their Mitzvah, they receive a certain level of holiness. Particularly, when one writes the Parshiyos, prepares the Batim, and sews the Parshiyos into them, the Tefillin receives the level of holiness of the Mochin of Chochma and Bina. However, only after a Jew actually wears them and fulfills the Mitzvah with them, is the level of Tosefes Mochin from above Keser drawn below.
Partner with Hashem:
One who wears Tefillin is considered a partner of Hashem in the creation of the world.
Elevates one’s prayer:
All of one’s prayers are elevated through one’s Tefillin. When one wears Tefillin during prayer the angels welcome it through announcing “Bring respect to the resemblance of the King.”
Subjugates the heart:
We place the Tefillin by the heart and by the head in order to subjugate the soul that is in the mind and the desires within the heart towards service of Hashem, as through donning Tefillin one remembers Hashem and diminishes his pleasures.
A combating tool for one who suffers from schizophrenia:
Wearing Tefillin helps one subjugate his mind and heart to be in tune with reality. It is hence a great method for battling schizophrenia. The illness of schizophrenia causes a person to have distortion of reality and confuse fact for fiction and fiction for fact. His emotions are linked to the false realities that his mind envisions and causes him to sway from one extreme to another. Wearing Tefillin is helpful in refining the mind and the heart and to recreate a healthy bond between them.
Merits the world to come:
One who wears Tefillin merits a portion in the world to come. The fire of Gihennim does not overtake him and all of his sins are forgiven.
Brings humility and fear of Heaven:
Wearing Tefillin brings one to humility and fear of heaven, and prevents one from thinking foreign thoughts. Rebbe Eliezer Ben Yaakov stated: Whoever has Tefillin on his head and Tefillin on his arm and Tzitzis on his garment, and a Mezuzah on his door is guaranteed not to sin, as the verse states “Vehachut Hameshulash Lo Bemiheira Yinatek” as well as the verse states “The angel of Hashem rests around those who fear Him, and save him from sin.” [This however only applies to one who internalizes the meaning behind the Tefillin that he is wearing. However, one who does not do so, it is as if he is placing the Tefillin on the wall or table. This is why the Talmud states “Tefillin in the head” and not “Tefillin on the head” as having the Tefillin simply on one’s head does not suffice.]
Places fear onto the nations:
The verse states “And all the nations of the land will see that the name of Hashem is written on you and they will fear you.” The Sages state that this statement refers to the head Tefillin, as the head Tefillin contains two letters of the three-letter name of Shakaiy. The Rosh explains that in merit of wearing Tefillin the people of war will be successful in killing the enemy. [This Talmudic dictum served as one of the main motivations behind the Rebbe’s Tefillin campaign which he began in 1967, just days before the six day war, in order to impose fear on the enemy.]
The power of the Tefillin Shel Rosh:
The Tefillin Shel Rosh is called in Kabbalah a Chosem Boleit, or a protruding inscription. This means as follows: All Mitzvos cause a Hamshacha, diffusion, of G-dliness below. This, however, will only be experienced in the future, after Moshiach comes. However, the Mitzvah of Tefillin Shel Rosh is so powerful, that it causes even now for Divine revelation to enter and effect the world. This is similar to prayer, which draws G-dliness below and changes decrees to heal an individual, and give Parnasa to an individual, and the like.
 See Admur 37:1; Ketzos Hashulchan 8:28; Igros Kodesh 1:300
 Admur ibid; Michaber 37:1; Rosh Hashanah 17a
 M”B 37:2; P”M 37 A”A 1 in name of Nachalas Tzevi 1; See Reishis Chochmah Shaar Hakedusha 6:54, 56
Other opinions: Some Poskim rule that one is only considered a Poshei Yisrael if he did not put on Tefillin his entire life. [Rif in Rosh Hashanah ibid, brought and negated in Reishis Chochmah ibid; Rambam Hilchos Teshuvah 3:5; Shaareiy Teshuvah of Rabbeinu Yona 3:11; Ran Rosh Hashanah 17a; Rabbeinu Chananel; Ittur in name of Teshuvos Hageonim]
 Rav in Rosh Hashanah ibid
 Rav Chaim Vital in Shaar Hakedusha 1:7, brought in Kaf Hachaim 37:6
 See Likkutei Sichos 6:271, printed in Shulchan Menachem 1:112
 M”A 37:1; See Machatzis Hashekel ibid; Beir Heiytiv 37:1
Other opinions: Some Poskim rule that even in such a case the person is included within Poshei Yisrael Begufan. [Beis Yosef in opinion of Tur; See Kaf Hachaim 37:5]
 Admur ibid; Rosh Tefillin 28
 Admur ibid; Rosh Tefillin 28
 The reason: This is learned from the verse “Lemaan Tehiyeh Toras Hashem Beficha” [Admur ibid; Kiddushin 35a]
 Admur ibid; Reish Lakish in Menachos 44a
 This does not just mean that he puts on the Tefillin, but that he is careful to guard all of its laws meticulously, and to purchase Mehudar Tefillin.
 Yafeh Lalev, brought in Kaf Hachaim 37:1
 Mishmeres Shalom Basra 6
 Admur 25:15; Tur 25; Rosh Tefillin 2
 P”M 25 A”A 8; Beis David 20; Ashel Avraham Openheimer
 Tiferes Yisrael Menachos 4:8
 Reishis Chochmah Shaar Hakedusha 6:55; Semag Asei 3; Tikkunei Zohar 2a
 Menachos 35b; See also Zohar Chayeh Saran 129a; Reishis Chochmah Shaar Hakedusha 6:49-51
 Mitzvas Tefillin
 Chayeh Sara 129a
 See Zohar ibid and Reishis Chochmah ibid
 Ayin Beis p. 367; See also Likkutei Torah Tazria p. 23
 Likkutei Torah Emor 1st Mamar p. 33; See also Toras Menachem 1984 Bo 3rd of Shevat
 Kiddushin 35a
 Midrash Tehillim 1:17; See Tosafus Rosh Hashanah 17a; Reishis Chochmah Shaar Hakedusha 6:52
 Printed in Sefer Hamamrim 5708 p. 271
 See Likkutei Sichos 16:499; Igros Kodesh 19:111
 Likkutei Sichos 1:39
 Ayin Beis p. 367; See also Siddur Im Dach p. 6b-15; Derech Mitzvosecha Mitzvas Tefillin p. 16b
 Rebbe Avin Bar Rav Ada in name of Rebbe Yitzchak in Brachos 6a
 Rav Chiya Bar Avin in Brachos ibid
 Rokeiach Bo
 Imrei Pinchas
 Tikkunei Zohar Tikun 47
 Sidur Admur; Admur 25:11
 Likkutei Sichos 36 p. 297; “Healthy in Body and in Spirit” Volume 3 p. 138
 Shimusha Raba
 Rambam 4:25
 Menachos 43b
 Brachos 6a
 Beir Mayim Chaim 1, brought in Ketzos Hashulchan 8 footnote 43; Taamei Haminhagim Tefillin 25; Sefas Emes Bo
 Devarim 28
 Rebbe Eliezer Hagadol in Menachos 35b; Brachos 6a
 See Rashi and Tosafus ibid
 See Rosh Halchos Tefillin 15
 See Sichas Parshas Bamidbar 24th Iyar, 5727, printed in Mivtzaim Kehalacha p. 26; See also Likkutei Sichos 6:271, printed in Shulchan Menachem 1:110
 Gloss in Derech Mitzvosecha p. 20b