Ba'al Shem Tov, Kuntres Meirat Einayim 70/בעל שם טוב על התורה·קונטרס מאירת עינים ע׳

1From the time of the Baal Shem Tov and on, when the Rectifications began to be accomplished by attaching oneself to G‑d-fearing people, and not through ascetic practices, the light of the Messiah began to shine. Nevertheless, if a person knows that he has the strength, he should afflict himself a little.Sheiris Yisroel, p. 17c