It is narrated from the Mother of the Believers, Sayyidah Aishah (may Allah be pleased with her), that she said: The Messenger of Allah (peace and blessings be upon him) said during the Farewell Hajj: "Had I not brought the sacrificial animal with me, I would certainly have come out of ihram (after performing Umrah)."
He (peace and blessings be upon him) had entered ihram for Umrah and Hajj together, so the people of knowledge held that it was the sacrificial animal (hady) that prevented him (peace and blessings be upon him) from coming out of the ihram of Umrah before performing Hajj, while those of his Companions (may Allah be pleased with them) who had not brought a sacrificial animal with them had come out of ihram.