The Messenger of Allah ﷺ said, "Every sin of the martyr is forgiven except debt."
أن رسول الله ﷺ قال: يغفر للشهيد كل ذنب إلا الدين.
Muslim reported it in the Book of Leadership (1886) from Zakariya bin Yahya bin Salih Misri, who said, Mufaddal (meaning Ibn Fadala) told us, from Ayyash (that is, Ibn Abbas Qatbani), from Abdullah bin Yazid Abu Abdul-Rahman Hublee, from Abdullah bin Amr, and he related it.In another version he has, from Saeed bin Abu Ayub, from Ayyash bin Abbas, "Being killed in the path of Allah atones for everything except debt."