Musannaf Ibn Abi Shayba 28:330

Waki' narrated to us, he said: Sufyan narrated to us, from Habib ibn Abi Thabit, from al-Mughirah ibn Shibl, from Jarir ibn Abdullah, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When a slave flees to the enemy, the covenant (dhimmah) is absolved from him."