The Mother of the Believers Hafsah (may Allah be pleased with her) said that in the year of the Farewell Hajj the Prophet (peace and blessings be upon him) ordered his wives "to come out of ihram." Sayyidah Hafsah (may Allah be pleased with her) said to him: What prevents you (peace and blessings be upon him) from coming out of ihram? He (peace and blessings be upon him) said: "I have matted my hair and garlanded my sacrificial animal, so I cannot come out of ihram until I have slaughtered my sacrifice."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9581