Musnad Ahmad 795:9

Bahz narrated to us, Hammam narrated to us, Qatadah narrated to us, from al-Hasan, from Jun ibn Qatadah, from Salamah ibn al-Muhabbaq, that he was with the Messenger of Allah, peace and blessings of Allah be upon him, on the expedition of Tabuk. He came upon a house in front of which was a hanging water skin. He asked for a drink, and it was said: "It is dead (i.e., the skin of an animal that died without slaughter)." He said: "Its tanning is its slaughter."