Raja' bin Haywah (may Allah have mercy on him) said: Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) wrote to Abu Ubaydah (may Allah be pleased with him) that whatever property the enemy takes possession of and the Muslims then recover, it must be returned to its original owner as long as it has not been divided.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18256