Musannaf Ibn Abi Shayba 16:1016

Abu Bakr narrated to us, he said: Abu Usamah narrated to us, from Ibn 'Awn, who said: The skins of leopards were mentioned in the presence of Muhammad [Ibn Sirin]. He said: "It is only disliked to pray upon them." And Muhammad did not see any harm in riding upon them. He said: "I do not know of anyone who abandoned these skins out of religious scruple."