I recently received a mailing from a major local Jewish organization that spoke about the “mitzvah of tikkun olam” which is manifest in performing acts of social justice. In my years of Torah study classes I never came across this mitzvah and am wondering if you could please provide the source. As always, I much appreciate your comments.
There are a number of classical works which enumerate the 613 mitzvos of the Torah,  and none of them count tikkun olam or, “repairing the world”, as one of the mitzvos. In fact, the phrase tikkun olam don’t even appear in the Torah, which certainly precludes this concept as being a “mitzvah.”
Tikkun olam, in fact, is a most profound Kabbalistic concept, which has its source in Rabbinical literature. To understand its meaning, it must be taken in context of how the Sages introduced it to us.
The most notable source is in the Aleinu prayer recited at the end of the prayer service, “…Letaken Olam Bemalchus Sha-dai…” or “to perfect the world in the kingdom of the Al-mighty.”
The Kabbalists explain this as follows: The world was purposely created imperfect to allow us the potential to perfect it, thereby becoming partners with the Al-mighty in the creation of the world. This allows us the opportunity to earn the goodness the Al-mighty wishes to bestow upon us, rather than simply to receive it as a gift, which is preferable for a number of reasons (which we may discuss at another time).
The 613 mitzvos were given to us as the “manufacturer’s manual” of what it is that needs to be “fixed” in the world. Every mitzvah which one performs perfects the individual performing it, and elevates the world as well, one step closer to its “tikkun.” The 613 mitzvos are comprised of 248 positive, corresponding to a count of our body parts and organs, and 365 “don’ts,” corresponding to the days of the year. What is the message in those parallels?
The message is: every body part and every day of the year needs its tikkun. Whether or not any given act effects a tikkun olam is contingent upon if that act constitutes a mitzvah. When the act is, indeed, a mitzvah, that act does much to affect the world in the spiritual realm in addition to the physical benefits of the act, and goes very far in eradicating the forces of evil and the control of the physical over the spiritual. This is true tikkun olam – Bemalchus Sha-dai, enhancing the Kingdom of G‑d.
Acts of social justice are often the right and praiseworthy thing to do. Jews may often feel compelled to perform such acts out of the refinement endowed to them through the performance of mitzvos and the study of Torah. However, that doesn’t render such an act tikkun olam, nor a mitzvah per se.
We at times may be misguided into thinking that such acts are even more important than the mitzvos themselves and miss the opportunity for real tikkun olam by replacing the true brand with a generic brand which doesn’t quite have the same ingredients. Social justice, when combined with the entire system of Torah and mitzvos, is like serving the entire cake with its icing. It reflects the complete Jew living with tikkun olam, and in addition taking the lead to help uplift the world to be a better place for all.
 Most notably the Rambam (Maimonides), Sefer Hachinuch (Book of Education, by R’ Avrohom Halevi) and others all written in the 12-1300s, and more recent ones such as The Concise Book of the Mitzvos (by R’ Yisroel Meir Hakohen, the renowned Chofetz Chaim, of pre-war Europe),