The Forty Hadiths on the Foundations of Islam and the Principles of Rulings, known as the Forty Hadiths of Nawawi, is a book containing forty noble prophetic hadiths. Al-Nawawi explained the reason for collecting the forty, saying:
Some scholars have compiled the forty hadiths on the fundamentals of religion, some on the branches, some on jihad, some on asceticism, and some on sermons. All of these are valid objectives, may Allah be pleased with those who seek them. I have found that compiling forty hadiths is more important than all of this. They are forty hadiths that encompass all of that, and each hadith is a major principle of the religion. Scholars have described it as the core of Islam, or as describing Islam, or a third of it, or something similar.
Then he committed these forty to be authentic, and he deleted their chains of transmission to make them easier to memorize.