Sayyidah Hafsah (may Allah be pleased with her) relates that I said: O Messenger of Allah! What is the matter with the people, that they have come out of ihram while you have not come out of ihram from your Umrah? He (peace and blessings be upon him) said: "I have matted my hair (talbid) and garlanded my sacrificial animal, so I will not come out of ihram until I have slaughtered."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19615