Musannaf Ibn Abi Shayba 8:1246

Abu Bakr narrated to us, he said: Sufyan ibn ‘Uyaynah narrated to us, from Muhammad ibn al-Munkadir, [who] heard Sa‘id ibn ‘Abd al-Rahman ibn Yarbu‘ informing from Juwaybir ibn al-Huwayrith, [who] heard Abu Bakr while he was standing at Quzah, and he was saying: "O people, set out! Set out!" Then he raised [his garment], and it is as if I am looking at his thigh, which had become uncovered from him prodding his camel with his camel-stick.