Sahih Bukhari
Minor Pilgrammage (Umra)
Volume: 003 / Book Number: 027 / Hadith Number: 7
Narrated Qatada:
I asked Anas (about the Prophet's 'Umra) and he replied, "The Prophet performed 'Umra when the pagans made him return, and Umra of al-Hudaibiya (the next year), and another 'Umra in Dhi-l-Qa'da, and another 'Umra in combination with his Hajj."