Musnad Ahmad 25:55

Sufyan narrated to us, from al-Zuhri, from Ubayd Allah ibn Abd Allah, from Ibn Abbas: "That the Prophet, may God bless him and grant him peace, went out on the day of the Conquest, and he fasted until, when he was at al-Kadid, he broke his fast." "And the latter of the actions of the Messenger of God, may God bless him and grant him peace, is what is to be taken." It was said to Sufyan: "Is his saying, 'The latter is what is to be taken,' from the speech of al-Zuhri or the speech of Ibn Abbas?" He said: "It is thus in the hadith."