Musannaf Ibn Abi Shayba 13:527

Abu Bakr narrated to us, he said: Abbad bin al-Awwam narrated to us, from Hajjaj, from Husayn al-Harithi, from al-Sha'bi, from al-Harith, from Ali, he said: Whoever hires a worker, he is a guarantor [for him].