It is narrated from Sayyiduna al-Hirmas bin Ziyad (may Allah be pleased with him); he said: I was riding behind my father, and I saw the Prophet (peace and blessings be upon him) on a camel, saying: "Labbayk, for Hajj and Umrah together."
Hadith Referenceالمعجم الكبير للطبراني / باب الهاء / 18754