It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) used to say: "This is an Umrah from which we have benefited. So whoever does not have a sacrificial animal (hady) with him, let him come out of ihram completely, for Umrah has entered into Hajj until the Day of Resurrection."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10999