Musannaf Ibn Abi Shayba 13:1182

Abu Bakr narrated to us, he said: Hatim ibn Isma'il narrated to us, from Ja'far, from his father, from Ali, who said: The foundling (al-manbudh) is free. If the one who raised him seeks his maintenance and he (the foundling) is wealthy, he shall return it to him. And if he (the foundling) is not wealthy, then what he (the raiser) spent on him is charity.