The Torah says "And you should tie them (the TEFILLIN) for a sign on your hand, and they should be ornaments between your eyes.
Every Jewish male must put on TEFILLIN. The TEFILLIN bear witness that the Shechinah rests on one who wear them. Indeed, he even resembles the Shechinah, as the Talmud tells us that (figuratively) G-d Himself puts on TEFILLIN.
The Talmud states: " Great is the merit of those who put on TEFILLIN", as Resh Lokish says: "whoever puts on TEFILLIN will live long." Rava says: "whoever puts on Talis and TEFILLIN and recites the Shema and Davvens, is promised a place in the world to come." Abaye says: "I guarantee him that the fire of hell will not harm him." Rav Pappa says: "I guarantee him that all his sins will be forgiven." The Zohar says: "whoever puts on TEFILLIN a voice calls out throughout all the worlds " give honor to the image of the king," becouse when a Jew puts on TEFILLIN godliness shines upon him etc.
Our Rabbis teach that there's no greater Mitzvas Assay (positive commandment) than that of TEFILLIN And that the Mitzvah of TEFILLIN is compared to the entire Torah. Therefore, when one puts on Tallis and TEFILLIN it is considered as if he has performed all 613 Mitzvos of the Torah, and it is tantamount to learning the Torah day and night diligently.
On the other hand, the punishment for not putting on TEFILLIN is awesome. I hesitate to write the bad things in store for one who fails to put on TEFILLIN, but this is only until he returns to G-d and starts putting on TEFILLIN, as it says "the place where a Baal Teshuvah stands a complete Tzadik cannot stand."