According to search-discovered classical Islamic scholarship, the Quranic concept of 'Ad-Din' (الدين) transcends the modern English term 'religion', referring to a comprehensive and divinely ordained way of life. The great exegete Al-Tabari explains that its Arabic root, د-ي-ن, encompasses the meanings of indebtedness, submission, and judgment, framing human existence as a sacred transaction with the Creator. This synthesis is powerfully articulated across the Quran's 26 key verses on the topic, which establish 'Ad-Din' as the singular, unified path of all prophets. Ibn Kathir's tafsir on verses 3:19 and 3:85 clarifies that Islam, meaning 'submission to Allah', is this one true Din, the culmination of all previous revelations. While verses like 2:256 affirm there is 'no compulsion in Din', Al-Qurtubi interprets this not as religious relativism, but as a statement on the nature of faith: its truth is so clear that it needs no coercion. Thus, Ad-Din is the complete framework for humanity's moral, spiritual, and social life, culminating in accountability on the Day of Judgment (Yawm ad-Din).