Sahih Bukhari
Manumission of Slaves
Volume: 003 / Book Number: 046 / Hadith Number: 706
Narrated 'Umar bin Al-Khattab:
The Prophet said, "The (reward of) deeds depend on intentions, and every person will get the reward according to what he intends. So, whoever migrated for Allah and His Apostle, then his migration will be for Allah and His Apostle, and whoever migrated for worldly benefits or for marrying a woman, then his migration will be for what he migrated for." (See Hadith No. 1, Vol. 1)