According to search-discovered classical Islamic scholarship, 'Al-Kitab' (الكتاب), or 'The Book', is a foundational Quranic concept representing the continuous stream of divine revelation bestowed upon humanity. Classical exegetes like Al-Tabari trace its linguistic root (k-t-b) to the act of writing and ordaining, signifying that revelation is a divinely decreed reality. Ibn Kathir's tafsir on verses such as 2:4 and 4:136 explains that 'Al-Kitab' encompasses all scriptures sent by God, including the Torah, the Gospel, and the Psalms, making belief in them an integral pillar of Islamic faith (Iman). The synthesis across 13 key verses shows a unified theme: while Muslims must believe in the divine origin of all Books, the Quran (also referred to as Al-Kitab) serves as the final, protected confirmation and criterion over them, correcting human alterations as highlighted in verse 2:79. Contemporary scholarship affirms that this concept establishes a shared heritage with the 'People of the Book' (Ahl al-Kitab) and solidifies the Quran’s role as the culmination of divine guidance.