Kriyas Shema that we say every Shacharis and Maariv is made up of three paragraphs. These three paragraphs are excerpts from Chumash but they are not written together in one place; the first paragraph, Shema Yisroel is written in Sefer Devarim in parshas Va’eschanan and speaks of our obligation to accept Hashem’s rule. The second paragraph is an excerpt from parshas Eikev and speaks of our obligation to perform mitzvos and the great reward we receive for this. The third paragraph is written in Sefer Bamidbar and speaks of the mitzvah to put tzitzis on a four-cornered garment and that Hashem took us out of Mitzrayim.

In the mishna (Brachos 13a), Rabbi Yehoshua ben Korchah asked: Why do we recite the paragraph of Shema before we recite the paragraph of Vehaya im shemoa? The answer is in order to first accept the yoke of Heaven’s rule and after that to accept the yoke of the mitzvos. And what is the reason that “Vehayah im shamoa” is said before “Vayomer,” which speaks about the mitzvah of tzitzis? Because the mitzvah of studying Torah, which is mentioned in the passage of “Vehayah im shemoa” applies both by day and by night, while the mitzvah of tzitzis applies only by day.

Tosafos asks: that he doesn’t understand Rabbi Yehoshua ben Karchah’s question of why do we recite the paragraph of Shema before we recite the paragraph of “Vehaya im shemoa?” The reason is simple … Shema is written in parshas Va’eschanan and “Vehayah im shemoa” is written at the end of parshas Eikev, 125 pesukim later! We, therefore, recite these two paragraphs in the order that they are written in Chumash.

Tosafos explains that Rabbi Yehoshua ben Korchah was bothered by the fact that the section of “Vehaya im shemoa” was written second—even though that it is written in the plural form and addresses all of klal Yisroel collectively—whereas the section of Shema is written in the singular.

Zera Shimshon argues that this answer is a little forced, because a section of the Torah being written in the plural is not a reason to be written before a section written in the singular.

Zera Shimshon, therefore, gives a different explanation in light of an incident written in Maseches Brachos (14b) that Rav once washed his hands, recited Shema, put on tefillin and davened, in that order.

The Gemara asks: Why did Rav recite Krias Shema before he put on tefillin and not like we do—to first put on tefillin and then recite Krias Shema?

The Gemara concludes that the halacha is really that one first puts on tefillin and then says Krias Shema. Rav did it in the reverse order simply because there was a technical problem; Rav didn’t have his tefillin with him. A messenger was meant to bring him his tefillin but they still didn’t arrive as the latest time that one can say Krias Shema approached. Therefore, even though the halacha is that one first puts on tefillin and then says Krias Shema, Rav said Krias Shema without his tefillin since he didn’t have them at the time he was meant to say Krias Shema.

Zera Shimshon learns from this Gemara that physically doing a mitzvah takes precedence over just learning about it.

Because of this, Rabbi Yehoshua ben Korchah asked that the second parsha, “Vehaya im shemoa,” which speaks of performing the mitzvos—should be recited before the section of Shema—to allude to the above idea that performing mitzvos precedes learning.

Rabbi Yehoshua ben Korchah answers that the doing of mitzvos only precedes regular learning, but the acceptance of the rule of Hashem is so important that it precedes the acceptance of doing the mitzvos.

A question still remains, though, if the acceptance of Hashem’s rule is so important: Why do we put on tefillin before we say Shema and accept upon ourselves the rule of Hashem? Just like Shema precedes “Vehaya im shemoa,” because accepting upon ourselves the rule of Hashem is so important, so too, it should precede physically putting on tefillin!

The answer is that wearing tefillin is not only an independent mitzvah, but it is also an integral part of the acceptance of Hashem’s rule. To such a degree, it is written in the Gemara (Brachos 14b) that “a man can completely accept Hashem’s rule” when he recites Krias Shema only if he also wears tefillin at that time. Since it is a necessary component of accepting Hashem’s rule, there is obviously no problem to put them on before saying Krias Shema.