Musannaf Ibn Abi Shayba 13:2396

Abu Bakr narrated to us, he said: Ibn ‘Awn narrated to us, from Ibn Sirin, from Shurayh, that he used to not return [a slave] for *al-adfan*, but he would return [a slave] for *al-abaq*. *Al-adfan* is the one who hides within the city, and *al-abaq* is the one who flees to his own land.