Muslims Must Repay Debts from Dār al-Harb

In al-Baḥr al-Zakhkhār al-Jāmiʿ li-Madhāhib ʿUlamāʾ al-Amṣār, under the Book of International Relations and Military Conduct (Kitāb al-Siyar), Imām Aḥmad ibn Yaḥyā ibn al-Murtaḍā (d. 840 AH / 1437 CE) discusses financial dealings between Muslims and non-Muslims in Dār al-Ḥarb (enemy territory).

He explains that a Muslim who borrows in Dār al-Ḥarb is obligated to repay what he has taken, since it was acquired through a legitimate contract of transaction. The contracts of Muslims with non-Muslims in such dealings are valid, and therefore repayment is binding.