Sahih Muslim Book 4, Hadith Number 2067.

Chapter : Merit of the funeral prayer and following the bier.

Abu Huraira reported Allah’s Messenger (may peace be upon him) as saying: He who offers prayer for the dead, for him is (the reward of) one qirat; and he who follows the bier till it is placed in the grave, for him (is the reward of) two qirats. I (Abu Hazim, one of the narrators) raid: Abu Huraira, what is this qirat? He said: It is like the hill of Uhud.