Muwatta Imam Malik (Riwayat Ibn al-Qasim)

And with this same chain (it is narrated from Sayyiduna Ibn Umar, may Allah be pleased with them both) that one of the wives of the Prophet (Sayyidah Hafsah, may Allah be pleased with her) asked the Messenger of Allah (peace and blessings be upon him): What is the reason that people have ended their ihram after performing ‘Umrah, but you have not yet ended your ihram after your ‘Umrah? The Prophet (peace and blessings be upon him) replied: “I have stuck my hair (with gum) and have designated the sacrificial animals, therefore I will not end my ihram until I have performed the sacrifice.”