Musnad Ahmad 30:2545

Ibn Numayr narrated to us, he said: Hajjaj—meaning Ibn Dinar—informed us, from Ja'far ibn Iyas, from 'Abd al-Rahman ibn Mas'ud, from Abu Hurayrah, who said: The Messenger of Allah (may Allah bless him and grant him peace) came out to us, and with him were Hasan and Husayn; this one on his shoulder, and this one on his shoulder. He was kissing this one at one time, and this one at another time, until he reached us. A man said to him: "O Messenger of Allah, you truly love them." He said: "Whoever loves them has loved me, and whoever hates them has hated me."