Musannaf Ibn Abi Shayba 27:472

Waki’ narrated to us, from Isra’il, from Abu Ishaq, from ‘Amr ibn Hubashi, who said: Al-Hasan ibn ‘Ali delivered a sermon to us after the death of ‘Ali and said: "A man has departed from you yesterday, whom the predecessors did not surpass in knowledge, and the successors will not attain. The Messenger of Allah, may Allah bless him and grant him peace, would give him the banner, and he would not return until Allah granted him victory."