Musnad Ahmad 25:1662

Rawh narrated to us, Shu'bah narrated to us, from Ya'qub ibn 'Ata', from his father, from Ibn 'Abbas: A sheep belonging to Maymunah died. The Prophet (peace and blessings of Allah be upon him) said: "Why did you not make use of its hide?" They said: "It is carrion." He said: "Tanning the hide is its purification."