Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates from the Messenger of Allah (peace and blessings be upon him) that he (peace and blessings be upon him) said: "This is an Umrah from which we have benefited, so whoever has no sacrificial animal with him should come out of ihram completely."
(b) "Umrah has indeed entered into Hajj until the Day of Resurrection."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8863