Musannaf Ibn Abi Shayba 20:25

Abu Bakr narrated to us, he said: Abu Mu’awiyah narrated to us, from al-Hajjaj, from Abu Sa’id al-A’sam: That the Messenger of Allah (may Allah bless him and grant him peace) decreed two judgments regarding the slave and his master. He decreed regarding the slave: If he exits from the Abode of War before his master, he is free, and if his master exits after him, he is not returned to him. And if the master exits before the slave from the Abode of War, then the slave exits after him, he is returned to his master.