Toil in Torah recreates the self

והנה חז"ל דרשו תלכו להיות עמלים בתורה.

Now Chazal expounded the words "if you walk [in My statutes]" to mean: that you toil and labor in Torah.

The pasuk's phrase "im bechukosai teileichu" is read not as mere observance but as ameilus baTorah — exerting oneself in the study of Torah.

וא"כ נכלל ג' המדרגות מחשבה דיבור מעשה.

If so, the three levels are included here — machshavah (thought), dibbur (speech), and maaseh (action).

The full avodah of a Jew operates on three planes — thought, speech, and deed — and all three are hinted at in this parsha.

כי מצותי תשמרו היא הרצון כמ"ש רש"י ע"מ לעשות וע"י דיבור ומחשבה זוכה אח"כ לעשות כי העשי' קשה מכולן.

For "you shall guard My mitzvos" is the ratzon (the will), as Rashi explains, "in order to do," and through speech and thought one then merits to come to the doing — since the deed is the hardest of them all.

Guarding the mitzvos begins as an inner resolve and intention; only by first fixing one's thought and speech does a person reach the level of carrying it out in action, which is the most demanding step.

ועיקר ע"מ לעשות הוא לתקן עצמותו כמ"ש חז"ל ועשיתם אותם כאילו עשיתם את עצמיכם.

And the essence of "in order to do" is to repair one's very self, as Chazal said: "and you shall do them" — as though you have made yourselves.

The true purpose of the deed is the tikkun of the person himself; by performing the mitzvos a Jew, as it were, recreates and refines his own being.

כי תרי"ג מצות מתקנים אברי וגידי האדם.

For the 613 mitzvos repair the limbs and sinews of a person.

The taryag mitzvos correspond to the 248 limbs and 365 sinews of the body, so that each mitzvah perfects a part of the human being.

ועי"ז זוכה לקבל הנפש ונשמה ונקרא ברי' חדשה.

And through this one merits to receive the nefesh and the neshamah, and is called a new creation (briah chadashah).

Once the body has been refined through the mitzvos, it becomes a fit vessel to receive higher levels of soul, and the person is reborn as a new creature.

והכל ע"י היגיעה בתורה כמ"ש בזוה"ק בפ' ישרצו המים כו' נפש חי':

And all of this comes about through the toil in Torah, as is written in the Zohar HaKadosh on the verse "let the waters swarm… [with] a living soul (nefesh chayah)."

It is specifically the exertion of ameilus baTorah that draws down the living soul into a person, just as the Zohar reads the "swarming waters" as the wellspring of living souls.

Summary: To "walk in Hashem's statutes" means to toil in Torah on all three planes — thought, speech, and action. The deed is the hardest, yet through it the taryag mitzvos repair the 248 limbs and 365 sinews, making the body a vessel that can receive the higher soul. In this way ameilus baTorah literally re-creates a person as a briah chadashah, a new being with a living nefesh.