Substance addiction is an important issue worldwide. In the Malagasy context, the Malagasy Lutheran Church (MLC) has institutions that treat people with substance addiction in places called toby, which are closely related to the Malagasy revival movements. Initially, the tobys primarily treated individuals with mental illnesses, but in recent decades, people struggling with substance addiction have become the majority of their patients. The tobys are among the primary places where Malagasy people seek help in coping with the devastating effects of substance addiction. In the tobys, religious practices like rituals of repentance are an important part of the treatment. Repentance is here understood according to the Lutheran tradition, where repentance means the person's transformation from inner repentance to a life of sanctification. The treatment thus aims not only at helping the patients to recover from mental illness and substance addiction but also at fostering a sustainable change. The question to be investigated in this paper is the understanding of the interaction between human agency and divine intervention in the tobys' treatment. This will be investigated through interviews with ex-patients who have experienced the treatment in the tobys as successful. Hopefully, this will help us understand how a religious ritual like repentance can be used in a meaningful way in the treatment of persons with substance addiction.