Musnad Abu Ya'la al-Mawsili 210:21

Abu Khaythama narrated to us, Jarir narrated to us, from Muhammad ibn Ishaq, from Nafi’, from Ibn ‘Umar, from Hafsa, who said: The Messenger of Allah (may Allah bless him and grant him peace) commanded us to exit the state of Ihram by performing ‘Umrah. I said, "O Messenger of Allah, what prevents you from exiting the state of Ihram?" He said, "Indeed, I have brought the sacrificial animal (hady) and I have matted my hair (labadtu)."