Musannaf Ibn Abi Shayba 28:1068

Abu Mu’awiyah narrated to us, from 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, then he is free, and if his master exits after him, he is not returned to him. And if the master exits from the Abode of War before the slave, then the slave exits after him, he is returned to his master.