From Sahih Muslim (Hadith 3014):
Ibn 'Abbas (Allah be pleased with them) reported Allah's Messenger (ﷺ) 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
Reference: Muslim 3014