Musannaf Ibn Abi Shayba 27:548

'Isa ibn Yunus narrated to us, from al-Awza'i, from Yahya ibn Abi Kathir, that the Prophet (may Allah bless him and grant him peace) heard the crying of al-Hasan and al-Husayn. He stood up in alarm and said, "Indeed, the child is a trial (fitnah). I stood up to him while I was not in my right mind."