According to the Talmud, compassion, besides being the hallmark of an ethical person, is the defining characteristic of being a Jew: "If someone is compassionate toward others, you can be sure that he is a descendent of our father Abraham, and if someone is not compassionate toward others, you can be sure that he is not a descendant of our father Abraham" (Beizah 32b). Sadly, one sometimes meets Jews who, according to this definition, are certainly not the spiritual descendants of Abraham.
— Joseph Telushkin, A Code of Jewish Ethics