Sahih Muslim Book 7, Hadith Number 2789.

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.

Safiyya hint Shaiba reported that ‘Aisha (Allah be pleased with her) said: Messenger of Allah, lo ! the people are returning with two rewards whereas I am returning with one reward. Thereupon he commanded ‘Abd al-Rahman b. Abu Bakr to take her to al-Tan’im. She (‘Aisha) said: He seated me behind him on his camel. She(further) stated: I lifted my head covering and took it off from my neck. He struck my foot as if he was striking the camel. I said to him: Do you find anyone here? She (further) said: I entered into the state of Ihram fond. ‘Umra till we reached the Messenger of Allah (may peace be upon him) and he was at Hasba.