Musnad Ahmad 25:793

'Affan narrated to us, Abu 'Awanah narrated to us, from Mansur, from Mujahid, from Tawus, from Ibn 'Abbas, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) set out from Medina to Mecca, and he fasted until he reached 'Usfan. Then he called for water and raised it to his hand so that the people could see him, and he broke his fast until he arrived in Mecca, and that was in Ramadan." And Ibn 'Abbas used to say: "The Messenger of Allah (peace and blessings of Allah be upon him) fasted and broke his fast, so whoever wishes may fast, and whoever wishes may break his fast."