Sahih Muslim
The Book of Pilgrimage (Kitab Al-Hajj)
Book Number: 007 / Hadith Number: 2769
'A'isha (Allah be pleased with her) said: We set out with the Messenger of Allah (may peace be upon him) just at the appearance of the new moon of Dhu'l- Hijja. We had no other intention but that of performing the Hajj, whereupon the Messenger of Allah (may peace be upon him) said: He who among you intends to put on Ihram for 'Umra should do so for 'Umra. The rest of the badith is the same.