Is usury (Riba) prohibited between Muslims and inhabitants of the House of War (Dar al-Harb)?
Chapter on Riba (Usury) and Exchange (Sarf)
Al-Mughni
Book of Sales
Primary text
Usury is prohibited in the House of War just as it is prohibited in the House of Islam. This is the position held by Malik, Al-Awza'i, Abu Yusuf, Al-Shafi'i, and Ishaq. The primary evidence for this prohibition rests upon the general commands of Allah prohibiting usury, specifically Quran 2:275, which states the prohibition on those who consume usury, and Quran 2:278, commanding believers to abandon what remains of usury. Furthermore, the general meaning of hadiths like "Whoever increases or has an increase has practiced Riba" is comprehensive and mandates prohibition. To hold that what is forbidden in the House of Islam remains forbidden even in the House of War is supported by analogy, such as the prohibition of usury between Muslims themselves. Arguments for exception based on the permissibility of the enemy's wealth are invalidated because the rule concerning usury is an established prohibition based on clear scripture and consensus, which cannot be overturned by a dubious, unverified report.
Supporting text
Abu Hanifa holds that usury does not apply between a Muslim and an enemy combatant in the House of War. Furthermore, a narration is cited stating, "There is no Riba between Muslims and the People of War in the House of War." The justification offered is that their wealth is permissible (mubah), and it is only the security pact (Aman) in the House of Islam that prohibits taking it, thus anything not covered by that pact remains permissible. This position is also supported by the argument that if two Muslims converted while in Dar al-Harb, no Riba would exist between them.