Sahih Muslim
The Book of Pilgrimage (Kitab Al-Hajj)
Book Number: 007 / Hadith Number: 2837
Hafsa (Allah be pleased with her) said that Allah's Apostle (may peace be upon him) commanded his wives that they should put off Ihram during the year of Hajj (at-ul-Wada'). whereupon she (Hafsa) said: What hinders you that you have not put off Ihram? Thereupon he said: I have stuck my hair and driven my sacrificial animal along with men and it is not permissible to put off Ihram (under this condition until I have sacrificed the animal.