Explanation of the Treatise Four Principles of Shirk

When the believer becomes aware that when Shirk is mixed with Tawheed it becomes corrupted just like when al-hadath corrupts purification then he should become aware that it is necessary to learn Tawheed and Shirk as it really is,  so he would not fall into Shirk.

Because Tawheed by definition is the religion of Allah, it is Islam, it is the guidance.  So when a person does any type of Shirk this nullifies his Islam, this nullifies his religion.