According to search-discovered classical Islamic scholarship, the ruling that contracts for future obligations should be in writing stems from Quran 2:282, the longest verse in the Quran, known as *Ayat al-Dayn* (The Verse of Debt). Classical commentators like Imam al-Tabari and Ibn Kathir explain that this verse provides divine guidance to ensure justice, prevent disputes, and provide clear evidence in financial dealings. While the command 'write it down' (*faktubūh*) is explicit, the majority of jurists interpret it as a strong recommendation (*mustahabb*) aimed at protecting the rights of all parties, rather than a strict obligation (*wajib*) for every transaction. The verse's detailed procedure—involving a just scribe, dictation by the debtor, and the presence of witnesses—creates a comprehensive framework that is more equitable in the sight of Allah, more reliable as testimony, and the surest way to prevent doubt. This principle remains a cornerstone of modern Islamic finance, emphasizing transparency and ethical conduct in all transactions.