Sahih Bukhari Volume 2, Book 26, Hadith Number 752.

Narated By Al-Miswar bin Makhrama and Marwan : The Prophet set out from Medina with over one thousand of his companions (at the time of the Treaty of Hudaibiya) and when they reached Dhul-Hulaifa, the Prophet garlanded his Hadi and marked it and assumed Ihram for ‘Umra.