Musannaf Ibn Abi Shayba 33:1370

Al-Hasan ibn Musa narrated to us, he said: Abu Hilal narrated to us, he said: Khalid ibn Riyāh narrated to us that Anas ibn Mālik was asked about a matter, so he said: "You must go to our master al-Hasan, so ask him." They said: "We are asking you, O Abu Hamzah, and you say 'Ask our master al-Hasan'?" He said: "Indeed, we heard and he heard, so we forgot and he memorized."