Sahih Muslim Book 7, Hadith Number 2673.

Chapter : The people of Medina are commanded to enter upon the state of ihram at a mosque in Dhu’l Hulaifa.

Salim reported that when it was said to Ibn ‘Umar (Allah be pleased with them) that the state of Ihram (commences from) al-Baida’ he said: Al-Baida’, you attribute lie about it to the Messenger of Allah (may peace be upon him). And the Messenger of Allah (may peace be upon him) did not enter upon the state of Ihram but near the-tree when his camel stood up with him.