Humayd narrates from Bakr, and he from Anas (may Allah be pleased with him), who said: I heard the Prophet (peace and blessings be upon him) saying the talbiyah for both Hajj and Umrah. Humayd said: Bakr said: I mentioned this to Ibn Umar (may Allah be pleased with them both), and he said that he (peace and blessings be upon him) said the talbiyah for Hajj alone. Then I met Anas (may Allah be pleased with him) and told him what Ibn Umar (may Allah be pleased with them both) had said, and he said: You regard us as nothing but children! I heard the Messenger of Allah (peace and blessings be upon him) saying: "Labbayka umratan wa hajjan" (Here I am, for Umrah and Hajj).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9002