Sahih Muslim Book 7, Hadith Number 2802.

Chapter : Performing Hajj and Umra separately.

Jabir b. ‘Abdullah (Allah be pleased with them) reported: We came with the Messenger of Allah (May peace be upon him) pronouncing Talbiya for Hajj, and the Messenger of Allah (May peace be upon him) commanded us to make (our Ihram) into that of Umra.