Hafsah, the wife of Allah's Messenger, may Allah be pleased with her, asked:

“Messenger of Allah, how come people have put off Ihram, whereas you have not put it off after your 'Umrah?” 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.”

Hadith number in Sahih Muslim [Arabic only]: 2161