This topic can not be stressed enough even though some people say we understand Tawheed! We are muslims! Not Mushriks, teach us other stuff that will gain us more benefit instead of adressing us as non muslims talking about Tawheed day in and day out! Shaykh Saaleh aale-Shaykh mentions in his explanation of kashf ash-Shubuhaat, the following story:

Shaykh-ul-Islam Muhammad ibn Abdul-Wahhaab was with his students and after having completed the study of his book 'Kitab at-Tawheed', he wished to start again the study of this book for the 3rd or 4th time.

His students said to him : "O Shaykh, we wish to study another book, a book of fiqh or hadith".

The Shaykh replied: "Why (do you wish to study another book)?".

His students: "We have in fact understood Tawheed, we want to study another science".

The Shaykh: "Wait, I shall give some thought to this".

A few days later, the shaykh came to the lesson with a troubled face. His students asked him the reason for it.

The shaykh explained that he'd come across something which angered him. His students asked what it was.

The Shaykh: "It has been related to me that the inhabitants of a house have sacrificed a rooster (for a Jinn) in front of their door. I have sent someone to confirm this affair".

Some time later, his students asked him about the affair that he had mentioned.

The Shaykh replied: "In fact, the inhabitants of this house did not sacrifice for other than Allaah, but it was someone who fornicated with his mother".

Shocked, his students exclaimed:"We seek refuge with Allaah! He fornicated with his mother? We seek refuge with Allaah! He fornicated with his mother...".

After mentioning this story, Shaykh Saleeh explained that Shaykh-ul-Islam told this story to show them that the statement "We understand Tawheed" is ignorance and is one of the greatest tricks of the Shaytaan.