Sayyiduna Anas bin Malik (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) calling the talbiyah for Hajj and Umrah together. Bakr bin Abdullah (may Allah have mercy on him) said: I told this to Sayyiduna Abdullah bin Umar (may Allah be pleased with them both), and he said: He (peace and blessings be upon him) called the talbiyah for Hajj only. He said: Then I met Sayyiduna Anas (may Allah be pleased with him) and told him this, and he said: They regard us as nothing but children! I myself heard the Messenger of Allah (peace and blessings be upon him) saying: 'Labbayka 'umratan wa hajjah' (Here I am for Umrah and Hajj).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8829