Mutarrif bin Abdullah (may Allah have mercy on him) said: Sayyiduna Imran bin Husayn (may Allah be pleased with him) said to me: Know that the Messenger of Allah (peace and blessings be upon him) combined Hajj and Umrah; then nothing was revealed about it in the Book (of Allah), and the Messenger of Allah (peace and blessings be upon him) did not forbid it. A man said about it, from his own opinion, whatever he wished.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15323