Musannaf Ibn Abi Shayba 27:556

Muttalib ibn Ziyad narrated to us, from Jabir, from Abu Ja'far, who said: Al-Hasan and Al-Husayn wrestled. The Messenger of Allah (peace and blessings of Allah be upon him) said, "Go on, Husayn!" Fatimah said, "It is as if he is more beloved to you?" He said, "No, but Jibril is saying, 'Go on, Husayn!'"