Musnad Ahmad 658:211

Mu'ammal narrated to us, Sufyan narrated to us, from Abu Ishaq, from Al-Bara' ibn 'Azib, who said: "The Messenger of Allah, peace and blessings of Allah be upon him, made a truce with the polytheists on the day of Al-Hudaybiyah upon three conditions: Whoever came to them from the Prophet, peace and blessings of Allah be upon him, they would not return him, and whoever came to us from them, we would return him to them. And upon the condition that the Prophet, peace and blessings of Allah be upon him, would come the following year with his companions, and they would enter Makkah as 'Umrah performers, and they would not stay except for three days, and they would not enter except with the carrying of weapons: the sword and the bow."