From Sahih Bukhari (Hadith 1524):
Narrated Ibn `Abbas:Allah's Messenger (ﷺ) made Dhul-Hulaifa as the Miqat for the people of Medina; Al-Juhfa for the people of Sham; Qarn-al-Manazil for the people of Najd; and Yalamlam for the people of Yemen; and these Mawaqit are for the people at those very places, and besides them for those who come through those places with the intention of performing Hajj and `Umra; and whoever is living within these boundaries can assume Ihram from the place he starts, and the people of Mecca can assume Ihram from Mecca
Reference: Bukhari 1524