Sahih Muslim Book 7, Hadith Number 2863.

Chapter : Permissibility of Umra during the mouth of Hajj.

Ibn ‘Abbas (Allah be pleased with them) reported Allah’s Messenger (may peace be upon him) as saying: This is the ‘Umra of which we have taken advantage. So he who has not the sacrificial animal with him should get out of the state of Ihram completely, for ‘Umra has been incorporated in Hajj until the Day of Resurrection,