Musannaf Ibn Abi Shayba 8:2441

Abu Bakr narrated to us, he said: Abu al-Ahwas narrated to us, from Abu Ya'fur, who said: I was walking with Ibn Umar and Ibn al-Hanafiyyah from Mina to Arafat. Ibn Umar would say the takbir (Allahu Akbar), and Ibn al-Hanafiyyah would say the talbiyah (Labbayk Allahumma Labbayk).