Sahih Muslim Book 7, Hadith Number 2666.

Chapter : The place where the pilgrims enter upon the state of Ihram.

Abu Zubair heard Jabir b. ‘Abdullah (Allah be pleased with them) as saying as he was asked about (the place for entering upon the) state of Ihram: I heard (and I think he carried it directly to the Apostle of Allah) him saying: For the people of Medina Dhu’l-Hulaifa is the place for entering upon the state of Ihram, and for (the people coming through the other way, i.e. Syria) it is Juhfa; for the people of Iraq it is Dbat al-‘Irq; for the people of Najd it is Qarn (al-Manazil) and for the people of Yemen it is Yalamlam.