Sahih Bukhari
Minor Pilgrammage (Umra)
Volume: 003 / Book Number: 027 / Hadith Number: 1
Narrated Abu Huraira:
Allah's Apostle said, "(The performance of) 'Umra is an expiation for the sins committed (between it and the previous one). And the reward of Hajj Mabrur (the one accepted by Allah) is nothing except Paradise."