“…They shall confess the sin they committed…” – Bamidbar 5:7

וְהִתְוַדּוּ אֶת חַטָּאתָם אֲשֶׁר עָשׂוּ – במדבר ה, ז

The Rambam writes in Sefer Hamitzvos: “The 73rd mitzvah is that we are commanded to verbally acknowledge the sins we have committed before G-d, exalted be He, when we repent from them… As the Torah states, ‘They shall confess the sin they committed.” Notably, the Rambam mentions teshuvah, repentance, as the circumstance under which one can fulfill the mitzvah of verbal confession, yet he does not enumerate teshuvah as a mitzvah unto itself.

The absence of teshuvah from the Rambam’s list of mitzvos raised the discussion among the later commentaries as to whether repentance is a mitzvah of its own; does one fulfill a mitzvah by repenting and neglect a mitzvah if he does not repent? If it is a mitzvah, why does the Rambam not list it among the six hundred and thirteen?

One explanation given is that teshuvah is indeed a mitzvah, but it is a general recommitment to fulfill all of G-d’s other commands. Therefore, the Rambam does not enumerate teshuvah among the six hundred and thirteen unique mitzvos, since it does not entail any unique activity that is not included in the other mitzvos.

This idea reflects the inner meaning of teshuvah and its relationship with the other mitzvos. Our Sages explain that 248 positive commandments and the 365 prohibitions correspond to the 248 limbs and 365 sinews in the human body (see Talmud, Makkos 23b; Zohar 1:170b). Chassidus explains that the soul is likewise comprised of six hundred and thirteen spiritual “limbs” or faculties, each corresponding to another mitzvah (Tanya, Chapter 4). A deficiency in the fulfillment of the one of the mitzvos causes a deficiency in the corresponding limb in one’s soul (Likutei Torah, Nitzavim).

Through Teshuvah, however, the deficient limbs of the soul can be repaired. This is because teshuvah, the profound desire and drive to reconnect with G-d, draws from the very essence of the soul, the source from which the individual limbs of the soul extend. Teshuvah thus draws new life into all the limbs of the soul, restoring them to their proper “health”. Accordingly, one can explain that only mitzvos that correspond to a specific limb in the soul are enumerated in the 613, but not teshuva, which stems from the essence of the soul and enlivens them all.

—Likutei Sichos vol. 38, pp. 18-23