Detailed Chapters Clarifying Tawhid, Minor Shirk & Major Shirk By Shaykh ʿAbdul ʿAzīz bin ʿAbdullāh bin ʿAbdur Raḥmān ar-Rājiḥī
It’s incumbent for the Muslim to be concerned with renewing his ʾĪmān (i.e., correct Islāmic faith) in the evening and the morning by pondering on the meaning of the statement of Tawḥīd lā ilāha illa Allāh since there’s no success except for the people of Tawḥīd. For it is the statement of Islām. So, the Muslim (Muwahhid) must learn about Tawḥīd, implement it, be aware of its position, reject Shirk which is the opposite of Tawḥīd, have a hatred for associating partners with Allāh as well as those who practice it. The Muslim must deem the one who commits major Shirk (knowingly) is a disbeliever of the true Islāmic Faith. The Muslim must also be aware of the position of Shirk.