Musannaf Ibn Abi Shayba 13:1933

Abu Bakr narrated to us, he said: Ibn ‘Uyaynah narrated to us, from al-Zuhri, who heard Sunayn Abu Jamilah saying: I found a foundling (manbudh), and my chief (arif) mentioned it to ‘Umar. So I came to him, and he said: "He is free, and his wala’ (right of inheritance/patronage) is yours, and his nursing is upon us."