Musannaf Ibn Abi Shaybah 35588 — A slave captured by the enemy, whom

It is narrated from Zuhrah bin Yazid al-Muradi that a man among the Muslims had a slave woman who ran away and joined the enemy (then some time later) the Muslims obtained spoils, and the slave woman's owner recognized her. Sayyiduna Abu Ubaydah (may Allah be pleased with him) wrote a letter to Sayyiduna Umar (may Allah be pleased with him) asking about this. Sayyiduna Umar (may Allah be pleased with him) wrote: If the fifth has not been taken from the slave woman and she has not been divided, she is to be returned to her owner; and if the fifth has been taken and the spoils have been divided, then leave her on that course (she remains with whoever received her).