Tafsir al-Kabir ("The Large Commentary"), also known as Mafatih al-Ghayb ("Keys to the Unknown") is a classical Islamic Tafsir book, written by the well-known Persian Islamic theologian and philosopher Muhammad ibn Umar Fakhr al-Din al-Razi (1149-1209). The book is an exegesis and commentary on the Qur'an, and is ten volumes in length. It is not unusual for contemporary works to use it as a reference.
One of [his] major concerns was the self-sufficiency of the intellect. [...] [He] believed [that] proofs based on tradition (hadith) could never lead to certainty (yaqin) but only to presumption (zann), a key distinction in Islamic thought. [...] [However] his acknowledgement of the primacy of the Qur'an grew with his years. [...] [Al-Razi's rationalism] undoubtedly holds an important place in the debate in the Islamic tradition on the harmonization of reason and revelation. In his later years, he also showed interest in mysticism, although this never formed a significant part of his thought.