Ba'al Shem Tov, Kuntres Meirat Einayim 50/בעל שם טוב על התורה·קונטרס מאירת עינים נ׳

1Our master the Baal Shem Tov said to his disciple, the Rabbi of Kalamaya, “I love the [Jew] who is least significant in your eyes more than you love your only son.”Leket Imrei Peninim, p. 208b