When Rabbi Sholom Ber of Lubavitch was four or five years old, his mother escorted him to see his grandfather, the Tzemach Tzedek , on the Shabbos of the Torah portion Vayeira , in order for him to receive his grandfather’s birthday blessing.

Upon entering his grandfather’s room the child began to cry. When his grandfather asked him why he was crying, he answered that he had learned in Cheder that G‑d appeared to Avraham. He was crying because he could not understand why G‑d appeared to Avraham but does not appear to us.

The Tzemach Tzedek responded: “When a Jew at the age of 99 decides that he should circumcise himself, he is deserving that G‑d should appear to him.”

The lesson of the Tzemach Tzedek ’s statement is that even a person who has engaged unremittingly in divine service for 99 years — as did Avraham — must also circumcise himself, i.e., he must take precautionary measures to guard against the coverings and concealments of the corporeal world and seek to remove them.

There is an additional factor involved: Adam was given six mitzvos , Noach received a seventh, and Avraham was given the mitzvah of circumcision. Since this mitzvah began with Avraham, it can be understood that it applied to him in particular.

Thus, Avraham’s decision at the age of 99 to circumcise himself not only involved a refinement in his manner of service, but made him realize that even after all those years he was still lacking something vital. Moreover, from this time on all his deeds would be accomplished in a higher manner.

This is in line with the comment of our Sages on the verse, “and be unblemished,”1 that G‑d told Avraham that as long as he was uncircumcised he was considered blemished.2 It is obvious that the difference between being blemished and unblemished applied to all aspects of Avraham, and not only to his “blemished” organ.

One of the meanings of “All the events that transpired with the Patriarchs serve as a sign to their progeny” is that the conduct of the Patriarchs in their performance of mitzvos paved the way and provided the fortitude for the Jewish people to perform the mitzvos after the Torah was given.

In order that the mitzvos performed by the Patriarchs be connected with those performed by the Jewish people after the Torah was given, there had to be at least one mitzvah that was similar to those performed by their children. This was the mitzvah of circumcision.

As opposed to Avraham’s performance of other mitzvos , this mitzvah was commanded by G‑d. Therefore the sanctity of the mitzvah remained in the physical object with which it was performed, similar to the sanctity remaining in objects with which mitzvos are performed subsequent to the giving of the Torah.

The commandment of circumcision was thus the one mitzvah that connected all the mitzvos performed by the Patriarchs with the mitzvos performed by their progeny after the Torah was given. It was specifically this mitzvah that made it possible for the mitzvos performed by the Patriarchs to provide fortitude to their children.

Accordingly, it is to be understood that Avraham’s decision to circumcise himself after 99 years of spiritual service involved much more than the realization that he was missing something vital, and that from now on all his actions would be whole and unblemished.

For it also involved the realization that all his previous actions were lacking; it was necessary that he circumcise himself so as to transform all his previous mitzvos as well, making them complete and unblemished.

There is a lesson here: A person must know that no matter how great he may be, he has yet to perform that degree of service which will render all his previous labors whole and complete.

Based on Likkutei Sichos , Vol. V, pp. 86-90.