Sayyiduna Hasan al-Basri (may Allah have mercy on him) says: "If a detachment goes out with the permission of the leader, then whatever wealth they obtain is theirs, and if they go out without permission, then their wealth will be divided into five shares and they will be equal to the common people."
Hadith Referenceسنن سعید بن منصور / كتاب الجهاد / 3861