Sahih Muslim Book 7, Hadith Number 2784.

Chapter : Types of Ihram- It is permissible to enter into the state of Ihram singularly for the sake of Hajj or for tamattu’ bi’l-‘umra ila’l-Hajj or for both hajj and ‘umra together.

‘Aisha (Allah be pleased, with her) reported: We went out with the Messenger of Allah (may peace be upon him) pronouncing Talbiya having no explicit intention of Pilgrimage or ‘Umra. The rest of the Hadith is the same.