Maliks Muwatta Book 20, Hadith Number 29.

Section : How to Enter Ihram.

Yahya related to me from Malik from Hisham ibn Urwa from his father that the Messenger of Allah, may Allah bless him and grant him peace, used to pray two rakas in the mosque at Dhu’l-Hulayfa, and then, when he had got on to his camel and it had stood up, he would begin doing talbiya.