Mitzvos complete the form of man

בפסוק אשר יעשה אותם האדם וחי בהם.

On the pasuk "which a man shall do, and live by them" (Vayikra 18:5).

The Sefas Emes takes up the verse that promises life through doing the mitzvos, and will explain what kind of "life" the mitzvos bestow.

דכתי' וייצר כו' את האדם עפר.

For it is written, "And He formed… the man from dust" (Bereishis 2:7).

Man's starting point is lowly — he is fashioned from the earth, sharing the material nature of all physical creatures.

וזה נפש בהמיות ואח"כ ויפח באפיו נ"ח ויהי האדם לנפש חי' שהוא כלי להמשיך החיות ובכח המצות יכול להמשיך החיות ואז נק' אדם.

This is the nefesh behamis (animal soul), and afterwards "He blew into his nostrils a living soul (nishmas chaim), and the man became a living being" — which is a vessel to draw down vitality; and by the power of the mitzvos he is able to draw down that vitality, and then he is called "adam."

At first man has only an animal soul; Hashem then breathes in a higher soul that makes him a vessel for divine life. Through mitzvos a person actively channels that vitality, and only then does he truly earn the title "adam."

כי הדם הוא הנפש.

For "the blood is the soul" (Devarim 12:23).

The Torah identifies the blood (dam) with the life-force, so the dam carries the vitality of the person.

לכן דרשו חז"ל לא תאכלו על הדם קודם שתתפללו על דמכם.

Therefore Chazal expounded "Do not eat over the blood" — before you have prayed over your blood (Berachos 10b).

Chazal read the prohibition as a hint: do not attend to your bodily needs (eating) before you have davened, elevating your very blood and life-force toward Hashem.

כי הא' מאדם היא המשכת החיות מרוח ונשמה על הדם להיות נקרא אדם.

For the alef of "adam" is the drawing of vitality from the ruach and neshamah onto the blood, so that he is called "adam."

The word "adam" is "dam" (blood) with an added alef. That alef represents the higher soul drawn down upon the blood; uniting the lofty soul with the physical life-force is what makes a person a complete "adam."

חי פי' בתוס' גבי כוס של ברכה חי פי' שלם.

"Chai" — Tosafos explain regarding the cup of berachah that "chai" means "complete/whole."

Tosafos (on the kos shel berachah of bentching) say that "chai" connotes wholeness, not merely "alive." So "v'chai bahem" speaks of a person made whole.

כי השלמת האדם ע"י המצות.

For the completion of man is through the mitzvos.

A person becomes whole — "chai" in the sense of complete — specifically by performing mitzvos.

וחי בהם שמשלים עי"ז צורת האדם.

"And live by them" — meaning that through them he completes the form of man.

"V'chai bahem" thus teaches that the mitzvos perfect the tzuras ha'adam, the full spiritual form a human being is meant to attain.

איתא בזוה"ק קוב"ה סתים וגלי' וכן התורה וכן ישראל.

It is brought in the Zohar HaKadosh: the Holy One, blessed be He, is concealed and revealed; and so too the Torah; and so too Yisrael.

The Zohar teaches a parallel structure — Hashem, the Torah, and Yisrael each have a hidden, inner dimension and a revealed, outer one.

וע"י המצות נמשך התגלות אור תורה במעשה המצוה.

And through the mitzvos, the revelation of the light of Torah is drawn into the act of the mitzvah.

Performing a mitzvah draws the concealed light of Torah out into the open, revealing it within the physical deed.

לכן כתי' אשר יעשה אותם האדם שאדם משלים המצוה בעשי'.

Therefore it is written "which a man shall do" — for the man completes the mitzvah through the doing.

The Torah stresses the human "doing" because it is precisely the physical act that brings the mitzvah to its fullness and reveals its inner light.

וכמו כן ע"י המצוה נגלה פנימיות נשמת האדם ברמ"ח אברים שבו.

And likewise, through the mitzvah the penimiyus (inner essence) of a person's neshamah is revealed in his 248 limbs.

The 248 mitzvos correspond to the 248 limbs; doing a mitzvah reveals the hidden soul within the body, drawing the inner neshamah out into one's physical limbs.

ועמ"ש לקמן בפ' קדושים:

And see what is written further on in Parshas Kedoshim.

The Sefas Emes refers the reader to his related discussion on Kedoshim, where the same theme of mitzvos drawing down hidden light is developed.

Summary: Man begins as mere dust with an animal soul, but the higher neshamah blown into him makes him a vessel for divine vitality. Through performing the mitzvos he draws that life-force onto his very blood — the alef that turns "dam" into "adam" — completing the form of man and revealing the concealed inner light of Hashem, Torah, and his own soul within his physical limbs.