Abu Dawud Book 4, 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.