Musnad Abu Ya'la al-Mawsili 155:375

Abu Hisham al-Rifa'i narrated to us, Ibn Fudayl narrated to us, Salim ibn Abi Hafsah narrated to us, from Abu Hazim, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever loves al-Hasan and al-Husayn has loved me, and whoever hates them has hated me."