Sunnan Abu Dawud Collection: ::Book Number 10:: Hadith # 1790
Narrated Mu'awiyah ibn AbuSufyan: Mu'awiyah said to the Companions of the Prophet (peace_be_upon_him): Do you know that the Apostle of Allah (peace_be_upon_him) prohibited from doing so and so (and he prohibited from) riding on the skins of leopards? They said: Yes. He again said: You know that he prohibited combining hajj and umrah. They replied: This we do not (know). He said: This was prohibited along with other things, but you forgot.