Sahih Muslim Book 27, Hadith 68
This hadith has been transmitted on the authority of Abu Tahir but with a slight variation of words.
For a faithful slave there are two rewards. By him in Whose hand is the life of Abu Huraira, but for Jihad 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.
When a slave fulfils obligation of Allah and obligation of his master, he has two rewards for him. I narrated this to Ka'b, and Ka'b said: (Such a slave) has no accountability, nor has a poor believer.