"Love your fellow Jew as yourself." (Vayikra 19:18)
The command to love our fellow Jews as ourselves includes caring for our
fellow Jews' physical needs, their honor, and their possessions (Rambam,
Hilchos Dei'os 6:3). Thus, there are three parts to the mitzvah: 1)
thoughts of love, 2)speaking praise, and 3)actions on others' behalf.
The Rambam further states, "One must relate his friend's praises and be
considerate of his money just as he is considerate of his own money and
wants to be honored himself"(ibid.).
This mitzvah is called the Great Rule of the Torah, because it encompasses
all of the other mitzvos (Rashi, Vayikra 19:18).