Musnad Abu Ya'la al-Mawsili 152:18

Abu Hisham al-Rifa'i narrated to us, he said: Abu Usama narrated to us, he said: Abu Hanifa narrated to us, from Qays ibn Muslim, from Tariq ibn Shihab, from Abdullah, who said: The Messenger of Allah (ﷺ) said: "The best of Hajj is the 'ajj and the thajj." As for the 'ajj, it is the talbiyah (reciting Labbayk Allahumma Labbayk). As for the thajj, it is the slaughtering of the sacrificial camels.