Musannaf Ibn Abi Shayba 33:1473

Yunus ibn Muhammad narrated to us, from Hammad ibn Zayd, from Ayyub, from Abu Qilabah, from Abu Muslim al-Khawlani, who said: The scholars are three: A man who lived by his knowledge, and people lived by it along with him. And a man who lived by his knowledge, and no one else lived by it. And a man whom people lived by his knowledge, while he destroyed himself.