Fiqh al-muamalat

Distinguished from fiqh al-ibadat (rituals of worship), fiqh al-muamalat governs contracts, sales, partnerships, loans, leases, and increasingly the structure of modern financial products.

The classical works of Imam al-Sarakhsi (Hanafi), Imam al-Shafi'i, and the Maliki Mudawwana are foundational references that modern Islamic finance still draws on.