Muwatta Imam Malik (Riwayat Ibn al-Qasim)

And with this chain (it is narrated from Sayyiduna Anas bin Malik, may Allah be pleased with him) that the Messenger of Allah, peace and blessings be upon him, entered Makkah in the year of the conquest, and there was a helmet on his head. When the Messenger of Allah, peace and blessings be upon him, removed the helmet, a man came and said: O Messenger of Allah! Ibn Khatal (a disbeliever) is clinging to the curtains of the Ka'bah. So the Messenger of Allah, peace and blessings be upon him, said: "Kill him." Ibn Shihab (al-Zuhri) says: The Messenger of Allah, peace and blessings be upon him, was not in the state of ihram that day.