Maliks Muwatta Book 20, Hadith Number 30.

Yahya related to me from Malik from Musa ibn Uqba that Salim ibn Abdullah heard his father say, “Your claim that the Messenger of Allah, may Allah bless him and grant him peace, entered ihram from this desert of yours is not true, because he only entered ihram from the mosque, i.e. the mosque of Dhu’l-Hulayfa.”