Sahih Muslim Book 7, Hadith Number 2833.

Chapter : The Qarin should not put off the Ihram but at the time when a Mufrid pilgrim takes it off.

Hafsa (Allah be pleased with her), the wife of Allah’s Apostle (may peace be upon him), said: Messenger of Allah, what about people who have put off Ihram whereas you have not put it off after your ‘Umra? He said: I have stuck my hair and have driven my sacrificial animal, and would not, therefore, put off Ihram until I have sacrificed the animal.