I asked, "Messenger of Allah, why have the people exited the state of ihram while you have not exited from your umrah?"He replied, "I have garlanded my sacrificial animal and matted my hair, so I will not exit ihram until I complete the Hajj."
حدثنا يحيى بن سعيد عن عبيد الله قال حدثني نافع عن ابن عمر
قلت يا رسول الله ما شأن الناس حلوا ولم تحل من عمرتك قال إني قلدت هديي ولبدت رأسي فلا أحل حتى أحل من الحج
Its chain of transmission is sahih. Bukhari narrated it, 3/422, no. 1566, in Hajj, as did Muslim, 2/902, no. 1229, Abu Dawud, 2/161, no. 1806, Ibn Majah, 2/1012, no. 3046, Nasai, 5/136, no. 2682, and Malik, 1/394, no. 180.