Musnad Ahmad 33:218

Rawh narrated to us, Zakariya ibn Ishaq narrated to us, Amr ibn Dinar narrated to us, I heard Jabir narrating: "That the Messenger of Allah (peace and blessings of Allah be upon him) was carrying the stones of the Kaaba with them, and he was wearing an izar (waist-wrapper). His uncle al-Abbas said to him, 'O son of my brother, if you were to loosen your izar and place it over your shoulders instead of the stones.' He said: 'So he loosened it and placed it over his shoulders, then he fell unconscious. He was never seen naked after that day.'"