What is the holy book of Islam known as?

The holy book of Islam is known as the Qur'an. It is considered the literal word of God (Allah) as revealed to the Prophet Muhammad through the Angel Gabriel. The Qur'an serves as the primary source of guidance for Muslims, encompassing spiritual, moral, and legal instructions and covering various aspects of life.

The Hadith, mentioned in the first option, are recorded sayings and actions of the Prophet Muhammad, which provide supplementary insights to the teachings of the Qur'an but are not considered scripture themselves. Sahih refers to a classification of certain hadith collections that are deemed authentic, but it does not refer to any text that serves as a holy book. Tafsir is the Arabic term for commentary or interpretation of the Qur'an, helping readers to understand its meanings and context, but again, it is not the holy book itself. Thus, the Qur'an stands out as the foundational text in Islam, making it the correct answer.