When the Jews encamped at Mount Sinai to receive the Torah, the verse states, “Israel encamped there opposite the mountain.” The word used for encamping, vayichan, is in singular, rather than vayachanu, plural. On this verse, Rashi comments, “Like one man, with one heart.” For that moment in history, the Jews experienced a true unification of spirit, a true ahavat Yisrael, love of their fellows.

The peace that reigned among them was a fitting preparation for the giving of the Torah. As the sage Hillel says, ahavat Yisrael is the foundation of the entire Torah. The rest is commentary.

The Baal Shem Tov, founder of the Chassidic movement, whose yahrtzeit (anniversary of his passing) is on Shavuot, was known for his ahavat Yisrael. In fact, he made it a cornerstone of his teachings. He stressed that one must love every Jew, regardless of whether one is simple or learned, righteous or average.

The Baal Shem Tov explained: Jews are like G-d’s Tefillin. G-d, too, lays Tefillin on His head and arm. His head Tefillin are the learned Jews, the intellectuals. The arm Tefillin are the simple Jews, who perform mitzvot out of simple faith.

When we don Tefillin, we wrap them around both the head and the arm. And which one is put on first? The arm Tefillin. The Baal Shem Tov uses this to illustrate the importance of even the simplest Jew to G-d. The arm Tefillin, symbolizing the simple Jew, is donned before the head Tefillin, which symbolizes the intellectual.

The Baal Shem Tov’s successor, Rabbi Dovber, the Maggid of Mezritsch, takes this concept a step further. One must love not only simple Jews but even wicked ones, reshaim.

The students of the Maggid used to take shifts to attend to him. When it was the turn of Rabbi Elimelech of Lizhensk, the Maggid turned to him and said, “Do you hear what they are discussing in the Heavenly Yeshivah? One must love a complete rasha the same as one loves a complete tzadik!

Rabbi Schneur Zalman of Liadi, founder of Chabad Chassidism, teaches further, that the Torah commands us to love our fellow just as we love ourselves. This mitzvah can be accomplished when we realize that our fellow Jew is actually one with us. The true identity of a Jew is not his body but his soul. And on the soul level, we are one, since we are all an actual part of G-d above. The more one identifies with the soul, and the less one identifies with the body, the easier it becomes to experience true love for our fellows.