Musannaf Ibn Abi Shayba 13:1087

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Isra’il narrated to us, from ‘Isa ibn Abi ‘Azzah, from al-Sha’bi, that he used to permit the testimony of young boys, and he would send for them and ask them about it.