Musannaf Ibn Abi Shayba 21:751

Fadl ibn Dukayn narrated to us, he said: Sufyan narrated to us, from Umayyah, from Dawud ibn Shabur, he said: A man said to Tawus, "Supplicate for us." He said, "I do not find in my heart at this moment [the necessary] fear [of Allah] so that I may supplicate for you."