Musannaf Ibn Abi Shayba 33:1101

'Affan narrated to us, he said: Hammad bin Zayd narrated to us, from 'Asim, he said: I heard Murriq al-'Ijli saying: "I have not seen anyone more learned in his piety, nor more pious in his learning, than Muhammad." He said: And Abu Qilabah said: "Direct him wherever you wish, and you will find him the most pious of you and the most in control of himself."