This article examines the question of exorcism and demonic possession in relation with the Malleus maleficarum. Meant to be a manual to be used by inquisitors, the Malleus presents a reflection on the therapeutic efficacy of exorcism, linked to the Biblical story of 1 Sam. 16:14-23 in which Saul, who became possessed, was healed by David and his cithara. According to the Malleus, the demon cannot change the soul of human beings, what it can do is lead it into delusion, or alter it by acting on its passive prior tendency to dementia. The therapeutic function of the exorcism lies in the reduction of such predisposition in the affective realm. Just as David’s cithara calmed Saul’s tormented soul, words pronounced by the exorcist calls upon the demon and forces the demon to stop its malevolent action, expelling it out of the body and soul of the possessed “in such a way that it does not return”.