Musannaf Ibn Abi Shayba 33:1458

Abu Khalid al-Ahmar narrated to us, from Sufyan, who said: Asceticism (*zuhd*) in the world is the shortening of hope, and it is not the wearing of wool. And he mentioned that al-Awza'i used to say: Asceticism in the world is the abandonment of being praised. He says: You perform a deed, not wanting people to praise you for it. And he mentioned that al-Zuhri used to say: Asceticism in the world is that the unlawful does not overcome your patience, and the lawful does not overcome your gratitude.