Musnad Ahmad 27:498

Hammad ibn Usamah narrated to us, from Ubaydullah ibn Umar, from Nafi’, from Ibn Umar: "That the Messenger of Allah (ﷺ), when he would put his foot into the stirrup and his she-camel stood upright with him, he would begin the Talbiyah from near the mosque of Dhu al-Hulayfah."