I saw the Messenger of Allah ﷺ mount his riding camel at Dhu al-Hulayfah, then begin the talbiyah the moment it stood upright with him.
أخبرني عيسى بن إبراهيم عن ابن وهب قال أخبرني يونس عن ابن شهاب أن سالم بن عبد الله أخبره أن
رأيت رسول الله ﷺ يركب راحلته بذي الحليفة ثم يهل حين تستوي به قائمة
ReferenceBukhari narrated it in the Hajj chapter, section titled "The saying of Allah Most High, 'they will come to you on foot...' etc.", hadith 1514, and Muslim in the Hajj chapter, section explaining that it is preferable to enter the state of ihram when one's mount sets off, hadith 29/1187, from the hadith of Ibn Wahb with the same wording. It is also found in al-Kubra, hadith 3739, and part of it was mentioned earlier at hadith 2684.