Sahih Muslim Book 7, Hadith Number 2793.

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.

Jabir b. ‘Abdullah reported that ‘Aisha (Allah be pleased with her) entered into the state of Ihram (separately) for ‘Umra while the Prophet (may peace be upon him) was performing Hajj. The rest of the Hadith is the same, but with this addition: The Messenger of Allah (may peace be upon him) was a person of gentle disposition, so when she (‘Aisha) wished for a thing, he accepted it (provided it did not contravene the teachings of Islam). So he (in pursuance of her desire for a separate ihram for Umra) sent her with ‘Abd al-Rahman b. Abu Bakr and she put on Ihram for ‘Umra at al-Tan’im. Matar and Abu Zubair (the two narrators amongst the chain of transmitters) said: Whenever ‘Aisha performed Hajj she did as she bad done along with Allah’s Apostle (may peace be upon him).