Sahih Al Bukhari Hadith Number 1541

Narrated Salim bin `Abdullah: I heard my father saying, “Never did Allah’s Messenger (peace be upon him) assume Ihram except at the Mosque, that is, at the Mosque of Dhul-Hulaifa.

25  Hajj (Pilgrimage)
Hadith number 1541
Volume no 2
Chapter: 20 (To recite talbiya and assume Ihram at the mosque of Dhul-Hulaifa)