Musnad Ahmad 795:3

Aswad ibn Amir narrated to us, Shu'bah narrated to us, from Qatadah, from al-Hasan, from a man whom he named, from Salamah ibn al-Muhabbaq, that the Prophet, peace and blessings of Allah be upon him, came to a household and asked for water. There was a water skin containing water, so they said, "It is dead (i.e., from an animal that died without slaughter), O Messenger of Allah." He said, "The tanning of the hide is its purification."