The turn of the nineteenth and twentieth centuries was a difficult period in the history of Morocco. Both the rulers, aware of their own weakness, and Muslim thinkers and scholars were aware of this. Among them, was a man partly associated with the court, but opposed to the passive politics of the sultans, Muhammad Ibn Ǧaʿfar al-Kattāni, a Salafi thinker and historian originating from the influential mystical Kattāniyya brotherhood. Many important Moroccan figures were associated with this brotherhood and to this day it plays a significant role in the social and political life of the country. In my article I will focus on the presentation of Al-Kattānī and his work Naṣīḥat ahl al-Islām (“Advice for Muslims”), first published in Fez in 1908. In it, the author points out the reasons for the weakness of Muslims that led to surrender hostile colonial forces. Characterising and analysing these reasons in depth, at the same time Al-Kattāni indicates ways to overcome them. So far, this work has not received much attention in Oriental studies, although it was a kind of guide for the Moroccan liberation movements that finally led to Morocco's independence in 1956.