Musannaf Ibn Abi Shayba 8:2419

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Ibrahim bin Yazid, from Muhammad bin ‘Abbad bin Ja’far al-Makhzumi, from Ibn ‘Umar, he said: The Messenger of Allah (ﷺ) said: "The best of Hajj is the *‘ajj* and the *thajj*." The *‘ajj* is the raising of voices with the *talbiyah*, and the *thajj* is the slaughtering of the sacrificial animals.