Love your fellow Yid

Mitzvah One - Loving another Jew

The Alter Rebbe said: The mitzva of ahavas yisroel extends to anyone born into am Yisroel, even if you have never met him How much more so does it extend to every member - man or woman of the Jewish community where you live, who belongs to your own community.
 (היום יום ג' אד"ר)

The Rebbe Maharash once told the Rebbe Rashab that the Alter Rebbe had mesirus nefesh and  invested tremendous effort so that all chassidim should literally be like one family, and that every chossid should seek out his friend's material good with  real love and affection, as if they were all children of one family.
(אג"ק מהוריי"צ ח"ד ע' לד)

The Rebbe once said that the first step for chassidim to bring about achdus Yisroel at large is to create achdus among themselves.

(תו"מ ח"ו ע' 124)