Musnad Ahmad 27:1608

Yunus narrated to us, Fulayh narrated to us, from Nafi’, from Ibn Umar, that the Messenger of Allah (ﷺ) matted his hair and offered a sacrificial animal. When he arrived in Makkah, he ordered his wives to exit the state of ihram. They said: "What is the matter with you that you do not exit the state of ihram?" He said: "I have garlanded my sacrificial animal and matted my hair, so I will not exit the state of ihram until I complete my Hajj and shave my head."