Abu Dawud
The Rites of Hajj
Book Number: 004 / Hadith Number: 1790
Narated By Mu'awiyah ibn AbuSufyan : Mu'awiyah said to the Companions of the Prophet (pbuh): Do you know that the Apostle of Allah (pbuh) 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.