Sahih Muslim Book 015, Hadith Number 4099.
Chapter : Reward of the slave when he is loyal to bit master and is good in worshipping Allah.
Abu Huraira reported Allah's Messenger (may peace be upon him) as saying: For a faithful slave there are two rewards. By him in Whose hand is the life of Abu Huraira, but for Jibad in the cause of Allah, and Pilgrimage and kindness to my mother, I would have preferred to die as a slave. He (one of the narrators in the chain of transmitters) said: This news reached us that Abu Huraira did not perform Pilgrimage until his mother died for (keeping himself constantly) in her service. This hadith has been transmitted on the authority of Abu Tahir but with a slight variation of words.