Ba'al Shem Tov, Nitzavim 4/בעל שם טוב על התורה·נצבים ד׳

1And you shall return to the L‑rd your G‑d, and listen to His voice… (Ibid. 30:2)When a person brings a candle into a dark room, the darkness completely disappears. So too, when a person repents; though at first he was in a dark place, when the light of Torah shines, the darkness vanishes completely.Degel Machane Ephraim, Likutim: Nitzavim