Musannaf Ibn Abi Shayba 18:680

Abu Bakr narrated to us, he said: Shareek narrated to us, from Jabir, from 'Amir, from 'Ali, who said: Whoever seeks the assistance of a young person, whether free or a slave, and he (the young person) suffers harm, then he (the one who sought assistance) is liable. And whoever seeks the assistance of an adult, he is not liable.