Musnad Ahmad 5:400

Abdullah narrated to us, Ahmad ibn Umar al-Waki‘i narrated to us, Zayd ibn al-Hubab narrated to us, al-Walid ibn Uqbah ibn Nizar al-Qaysi narrated to us, Simak ibn Ubayd ibn al-Walid al-‘Absi narrated to me, he said: I entered upon Abd al-Rahman ibn Abi Layla, and he narrated to me that he witnessed Ali at al-Rahbah. He said: "I adjure by Allah any man who heard the Messenger of Allah, peace and blessings of Allah be upon him, and witnessed him on the day of Ghadir Khumm, to stand up; and let no one stand except those who saw him." Twelve men stood up and said: "We saw him and heard him when he took his hand and said: 'O Allah, befriend whoever befriends him, be hostile to whoever is hostile to him, aid whoever aids him, and forsake whoever forsakes him.'" Everyone stood up except for three who did not stand, so he invoked [a curse] against them, and his supplication afflicted them.