Sahih Bukhari
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
Volume: 005 / Book Number: 059 / Hadith Number: 556
Narrated Ibn Abi Aufa:
When Allah's Apostle performed the 'Umra (which he performed in the year following the treaty of Al-Hudaibiya) we were screening Allah's Apostle from the infidels and their boys lest they should harm him.