From Moshe Hallamish, “An Introduction to the Kabbalah,” State University of New York (SUNY) Press, 1999 (trans. Ruth Bar-Ilan), Chapter 4. (End notes not included.)
The practice of equanimity originated in Greek culture, and the form it takes in Jewish mysticism differs in some respects from the original concept. Equanimity is mentioned in Bahya ibn Pakuda's Hovot ha-Levavot, which displays Sufi influence, as well as in the literature of the Ashkenazi Hasidim and in the kabbalistic works of Rabbi Isaac of Acre and others. I will not go into detail about the specific differences between the authors in approaching this phenomenon (while some maintain that equanimity must precede solitude with God, others subscribe to the opposite view). At any rate, the essence of equanimity is absolute impartiality and indifference to the mockery or admiration of others. The individual is so attached to the world on high that the way he is treated by people has no impact on him.
The element of impartiality stands out in an early Hasidic exhortation to embrace equanimity. In Sava'at ha-RiBaSH -- a work that is attributed to the Besht (R. Israel Ba'al-Shem-Tov), but clearly belongs to the school of his disciple, Rabbi Dov Baer of Mezhirech -- the following passage appears in the beginning of the text: "'Shiviti ha-Shem le-Negdi Tamid [I have set the Lord always before me]' (Psalms 16:8) -- shiviti derives from hishtavut, 'equanimity.' Whatever happens, all is equal to him, whether people praise him, or are contemptuous of him. And the same is true of other things, including the food he eats -- whether it is delicacies or plain food -- all is equal in his eyes, since the Evil Urge is completely removed from him. And he reacts to everything that happens to him by saying, 'this comes from Him, the Blessed One, and if He finds it proper,' etc. And his intention is purely and wholly for the sake of heaven, without any questioning on his part. Now this is a very high [spiritual] level.”
In various works, indifference assumes an extreme form. Though these works concern not equanimity, but solitude and communion with God (hitbodedut and devekut), these states entail forsaking one's family members and failure to support them. Such measures may seem to us too drastic, perhaps even somewhat cruel, but it is the price paid by many mystics. For example, Rabbi Shem Tov ibn Gaon writes: "The essence of [the mystic's] life essentially consists in ascending from earthly dwelling to celestial dwelling, to be sustained by the splendor of the Divine Presence and not to feel for his sons and other members of his family, out of his exceedingly strong devotion to God." Similarly, Rabbi Menahem Mendel of Vitebsk, the great Hasidic leader of the second half of the eighteenth century, recommends the Hasidic Jew "to further the enquiry of divine Wisdom ... to treat himself as if he were non-existent, in total renunciation of his body and soul ... and wherever he is, to desire nothing but Him, may His name be blessed ... for he has nothing to do with himself in terms of how and what he is ... once he has completely annihilated his self by contemplating the greatness of the Creator." Rabbi Shneur Zalman of Lyady, the disciple and companion of Rabbi Menahem Mendel, followed along the same lines when he preached "to let alone and abandon everything one has, from things of the soul to things of the flesh, and to renounce everything in order to attach oneself to the Blessed One with devotion, ardent desire and exalted delight. And there should be nothing to prevent this either from the inside or from the outside, whether physical or spiritual, whether money matters or family concerns."