Arfajah narrates from his father: When Sayyiduna Ali (may Allah be pleased with him) had killed the people of Nahrawan, he went round their camp, and whoever recognised anything (as his own) took it, until a cooking pot remained; then I saw that it too was taken afterwards. And Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says that the wealth of the Khawarij is not spoils (ghanimah).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16757