The Three Principles (Al Usool Ath Thalaathah) by Muhammad ibn Abdil Wahhaab, coveres the three questions we will be asked in our graves once we die:
“WHO IS YOUR LORD? WHAT IS YOUR RELIGION? WHO IS YOUR PROPHET?”
Shaykh Saalih al Fawzaan said in his explanation of the book:
“So before us is this treatise – the treatise “The Three Fundamental Principles” – and it is a tremendous treatise which is brief, supported by evidences from the Book of Allaah and the Sunnah of his Messenger sall Allaahu ‘alaihi wa sallam.
And this small treatise is about a tremendous fundamental matter from the fundamentals of Islaam, and it is ‘aqeedah – creed and belief. And the scholars give importance to these brief works, authoring them and exerting themselves in keeping them brief and refining them; then they would encourage their students to memorise them so that they should remain fundamental assets for them and a store of provision for them from which they can derive benefit, and through which they bring benefit to others.
And beginning with these shorter works is the foundation for the students of knowledge, so the student of knowledge should begin by learning little by little, taking from the initial points of knowledge and its fundamentals and then proceeding in stages through it.”
Or Alternatively click on the following: Arabic Text of Usool ath-Thalaatha