וְאָֽהַבְתָּ֥ לְרֵעֲךָ֖ כָּמ֑וֹךָ (Leviticus19:18)
One is to love your friend as yourself. It has been pointed out that there are two words in lashon hakodesh for saying friend; chaver and re’a. The difference is that chaver means someone who is similar to you. Chaver shares a root with the word chibur (to join/connect) and chabura (a gathering) - a chaver is someone who is thus easy to befriend because he is just like you.
But a re’a is someone who is different to you; he might have different goals, different viewpoints, and a different personality. For example a bride and groom are called re’imahuvim. Man and woman are different species, to say the least. Therefore, in choosing to use the word re’a, the Torah is commanding us to love even someone who is rather different to you.